diff --git a/common/dialogs/panel_setup_netclasses.cpp b/common/dialogs/panel_setup_netclasses.cpp
index 765825ede5..7b8ba1019a 100644
--- a/common/dialogs/panel_setup_netclasses.cpp
+++ b/common/dialogs/panel_setup_netclasses.cpp
@@ -119,10 +119,8 @@ PANEL_SETUP_NETCLASSES::PANEL_SETUP_NETCLASSES( wxWindow* aParentWindow, EDA_DRA
         // as this initial width is sometimes strange depending on the language (wxGrid bug?)
         int const min_width =  m_netclassGrid->GetVisibleWidth( i, true, true );
 
-        int const weighted_min_best_width =
-                        ( i == GRID_LINESTYLE )
-                        ? min_best_width * 3 / 2
-                        : min_best_width;
+        int const weighted_min_best_width = ( i == GRID_LINESTYLE ) ? min_best_width * 3 / 2
+                                                                    : min_best_width;
 
         m_netclassGrid->SetColMinimalWidth( i, min_width );
 
@@ -172,7 +170,6 @@ PANEL_SETUP_NETCLASSES::PANEL_SETUP_NETCLASSES( wxWindow* aParentWindow, EDA_DRA
 
     m_netclassGrid->SetAutoEvalCols( { GRID_WIREWIDTH,
                                        GRID_BUSWIDTH,
-
                                        GRID_CLEARANCE,
                                        GRID_TRACKSIZE,
                                        GRID_VIASIZE,
@@ -325,6 +322,8 @@ bool PANEL_SETUP_NETCLASSES::TransferDataToWindow()
         row++;
     }
 
+    AdjustAssignmentGridColumns( GetSize().x * 3 / 5 );
+
     return true;
 }
 
@@ -651,16 +650,15 @@ void PANEL_SETUP_NETCLASSES::AdjustAssignmentGridColumns( int aWidth )
     // Account for scroll bars
     aWidth -= ( m_assignmentGrid->GetSize().x - m_assignmentGrid->GetClientSize().x );
 
-    // Set className column width to original className width from netclasses grid
-    int classNameWidth = m_originalColWidths[ 0 ];
-    m_assignmentGrid->SetColSize( 1, m_originalColWidths[ 0 ] );
+    int classNameWidth = 160;
+    m_assignmentGrid->SetColSize( 1, classNameWidth );
     m_assignmentGrid->SetColSize( 0, std::max( aWidth - classNameWidth, classNameWidth ) );
 }
 
 
 void PANEL_SETUP_NETCLASSES::OnSizeAssignmentGrid( wxSizeEvent& event )
 {
-    AdjustAssignmentGridColumns( event.GetSize().GetX());
+    AdjustAssignmentGridColumns( event.GetSize().GetX() );
 
     event.Skip();
 }
diff --git a/common/dialogs/panel_setup_netclasses_base.cpp b/common/dialogs/panel_setup_netclasses_base.cpp
index cd0545f7ca..a39b152837 100644
--- a/common/dialogs/panel_setup_netclasses_base.cpp
+++ b/common/dialogs/panel_setup_netclasses_base.cpp
@@ -129,7 +129,7 @@ PANEL_SETUP_NETCLASSES_BASE::PANEL_SETUP_NETCLASSES_BASE( wxWindow* parent, wxWi
 	m_assignmentGrid->SetMargins( 0, 0 );
 
 	// Columns
-	m_assignmentGrid->SetColSize( 0, 400 );
+	m_assignmentGrid->SetColSize( 0, 360 );
 	m_assignmentGrid->SetColSize( 1, 160 );
 	m_assignmentGrid->EnableDragColMove( false );
 	m_assignmentGrid->EnableDragColSize( true );
diff --git a/common/dialogs/panel_setup_netclasses_base.fbp b/common/dialogs/panel_setup_netclasses_base.fbp
index 05582983d2..991b9f3784 100644
--- a/common/dialogs/panel_setup_netclasses_base.fbp
+++ b/common/dialogs/panel_setup_netclasses_base.fbp
@@ -766,7 +766,7 @@
                                                                     <property name="col_label_values">&quot;Pattern&quot; &quot;Net Class&quot;</property>
                                                                     <property name="col_label_vert_alignment">wxALIGN_CENTER</property>
                                                                     <property name="cols">2</property>
-                                                                    <property name="column_sizes">400,160</property>
+                                                                    <property name="column_sizes">360,160</property>
                                                                     <property name="context_help"></property>
                                                                     <property name="context_menu">1</property>
                                                                     <property name="default_pane">0</property>
diff --git a/common/widgets/wx_treebook.cpp b/common/widgets/wx_treebook.cpp
index bc4f32ba05..5207da231d 100644
--- a/common/widgets/wx_treebook.cpp
+++ b/common/widgets/wx_treebook.cpp
@@ -90,7 +90,7 @@ bool WX_TREEBOOK::AddLazySubPage( std::function<wxWindow*( wxWindow* aParent )>
 }
 
 
-wxWindow* WX_TREEBOOK::ResolvePage( int aPage )
+wxWindow* WX_TREEBOOK::ResolvePage( size_t aPage )
 {
     wxWindow* page = GetPage( aPage );
 
diff --git a/eeschema/dialogs/dialog_schematic_setup.cpp b/eeschema/dialogs/dialog_schematic_setup.cpp
index 0851b75d82..a7fa200c9d 100644
--- a/eeschema/dialogs/dialog_schematic_setup.cpp
+++ b/eeschema/dialogs/dialog_schematic_setup.cpp
@@ -1,7 +1,7 @@
 /*
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
- * Copyright (C) 2020-2022 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2020-2023 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software: you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
@@ -34,60 +34,88 @@
 #include <settings/settings_manager.h>
 #include "dialog_schematic_setup.h"
 #include "panel_template_fieldnames.h"
-#include <wx/treebook.h>
 
 
 DIALOG_SCHEMATIC_SETUP::DIALOG_SCHEMATIC_SETUP( SCH_EDIT_FRAME* aFrame ) :
         PAGED_DIALOG( aFrame, _( "Schematic Setup" ), true,
                       _( "Import Settings from Another Project..." ) ),
-        m_frame( aFrame ),
-        m_severities( nullptr )
+        m_frame( aFrame )
 {
-    PROJECT_FILE&       project = aFrame->Prj().GetProjectFile();
-    SCHEMATIC&          schematic = aFrame->Schematic();
-    SCHEMATIC_SETTINGS& settings = schematic.Settings();
-
     SetEvtHandlerEnabled( false );
 
-    m_formatting = new PANEL_SETUP_FORMATTING( m_treebook, aFrame );
-
-    m_fieldNameTemplates = new PANEL_TEMPLATE_FIELDNAMES( m_treebook,
-                                                          &settings.m_TemplateFieldNames );
-
-    m_pinMap = new PANEL_SETUP_PINMAP( m_treebook, aFrame );
-
     m_pinToPinError = ERC_ITEM::Create( ERCE_PIN_TO_PIN_WARNING );
-    m_severities = new PANEL_SETUP_SEVERITIES( this, ERC_ITEM::GetItemsWithSeverities(),
-                                               schematic.ErcSettings().m_ERCSeverities,
-                                               m_pinToPinError.get() );
-
-    m_textVars = new PANEL_TEXT_VARIABLES( m_treebook, &Prj() );
-
-    m_netclasses = new PANEL_SETUP_NETCLASSES( this, aFrame, project.NetSettings(),
-                                               schematic.GetNetClassAssignmentCandidates(), true );
-
-    m_buses = new PANEL_SETUP_BUSES( m_treebook, aFrame );
 
     /*
      * WARNING: If you change page names you MUST update calls to ShowSchematicSetupDialog().
      */
 
     m_treebook->AddPage( new wxPanel( GetTreebook() ), _( "General" ) );
-    m_treebook->AddSubPage( m_formatting, _( "Formatting" ) );
-    m_treebook->AddSubPage( m_fieldNameTemplates, _( "Field Name Templates" ) );
+
+    m_formattingPage = m_treebook->GetPageCount();
+    m_treebook->AddLazySubPage(
+            [this]( wxWindow* aParent ) -> wxWindow*
+            {
+                return new PANEL_SETUP_FORMATTING( aParent, m_frame );
+            }, _( "Formatting" ) );
+
+    m_fieldNameTemplatesPage = m_treebook->GetPageCount();
+    m_treebook->AddLazySubPage(
+            [this]( wxWindow* aParent ) -> wxWindow*
+            {
+                SCHEMATIC_SETTINGS& settings = m_frame->Schematic().Settings();
+                return new PANEL_TEMPLATE_FIELDNAMES( aParent, &settings.m_TemplateFieldNames );
+            }, _( "Field Name Templates" ) );
 
     m_treebook->AddPage( new wxPanel( GetTreebook() ), _( "Electrical Rules" ) );
-    m_treebook->AddSubPage( m_severities, _( "Violation Severity" ) );
-    m_treebook->AddSubPage( m_pinMap, _( "Pin Conflicts Map" ) );
+    m_treebook->AddLazySubPage(
+            [this]( wxWindow* aParent ) -> wxWindow*
+            {
+                ERC_SETTINGS& ercSettings = m_frame->Schematic().ErcSettings();
+                return new PANEL_SETUP_SEVERITIES( aParent, ERC_ITEM::GetItemsWithSeverities(),
+                                                   ercSettings.m_ERCSeverities,
+                                                   m_pinToPinError.get() );
+            }, _( "Violation Severity" ) );
+
+    m_pinMapPage = m_treebook->GetPageCount();
+    m_treebook->AddLazySubPage(
+            [this]( wxWindow* aParent ) -> wxWindow*
+            {
+                return new PANEL_SETUP_PINMAP( aParent, m_frame );
+            }, _( "Pin Conflicts Map" ) );
 
     m_treebook->AddPage( new wxPanel( GetTreebook() ), _( "Project" ) );
-    m_treebook->AddSubPage( m_netclasses, _( "Net Classes" ) );
-    m_treebook->AddSubPage( m_buses, _( "Bus Alias Definitions" ) );
-    m_treebook->AddSubPage( m_textVars, _( "Text Variables" ) );
+
+    m_netclassesPage = m_treebook->GetPageCount();
+    m_treebook->AddLazySubPage(
+            [this]( wxWindow* aParent ) -> wxWindow*
+            {
+                SCHEMATIC& schematic = m_frame->Schematic();
+                return new PANEL_SETUP_NETCLASSES( aParent, m_frame,
+                                                   m_frame->Prj().GetProjectFile().NetSettings(),
+                                                   schematic.GetNetClassAssignmentCandidates(),
+                                                   true );
+            }, _( "Net Classes" ) );
+
+    m_busesPage = m_treebook->GetPageCount();
+    m_treebook->AddLazySubPage(
+            [this]( wxWindow* aParent ) -> wxWindow*
+            {
+                return new PANEL_SETUP_BUSES( aParent, m_frame );
+            }, _( "Bus Alias Definitions" ) );
+
+    m_treebook->AddLazySubPage(
+            [this]( wxWindow* aParent ) -> wxWindow*
+            {
+                return new PANEL_TEXT_VARIABLES( aParent, &Prj() );
+            }, _( "Text Variables" ) );
 
     for( size_t i = 0; i < m_treebook->GetPageCount(); ++i )
         m_treebook->ExpandNode( i );
 
+    // This is unfortunate, but it's the cost of lazy-loading the panels
+    m_treebook->SetMinSize( wxSize( 920, 460 ) );
+    m_treebook->SetInitialSize( wxSize( 920, 460 ) );
+
     SetEvtHandlerEnabled( true );
 
     finishDialogSettings();
@@ -148,19 +176,34 @@ void DIALOG_SCHEMATIC_SETUP::onAuxiliaryAction( wxCommandEvent& event )
     file.m_SchematicSettings->LoadFromFile();
 
     if( importDlg.m_FormattingOpt->GetValue() )
-        m_formatting->ImportSettingsFrom( *file.m_SchematicSettings );
+    {
+        static_cast<PANEL_SETUP_FORMATTING*>( m_treebook->ResolvePage( m_formattingPage ) )
+                ->ImportSettingsFrom( *file.m_SchematicSettings );
+    }
 
     if( importDlg.m_FieldNameTemplatesOpt->GetValue() )
-        m_fieldNameTemplates->ImportSettingsFrom( &otherSch.Settings().m_TemplateFieldNames );
+    {
+        static_cast<PANEL_TEMPLATE_FIELDNAMES*>( m_treebook->ResolvePage( m_fieldNameTemplatesPage ) )
+                ->ImportSettingsFrom( &otherSch.Settings().m_TemplateFieldNames );
+    }
 
     if( importDlg.m_PinMapOpt->GetValue() )
-        m_pinMap->ImportSettingsFrom( file.m_ErcSettings->m_PinMap );
+    {
+        static_cast<PANEL_SETUP_PINMAP*>( m_treebook->ResolvePage( m_pinMapPage ) )
+                ->ImportSettingsFrom( file.m_ErcSettings->m_PinMap );
+    }
 
     if( importDlg.m_SeveritiesOpt->GetValue() )
-        m_severities->ImportSettingsFrom( file.m_ErcSettings->m_ERCSeverities );
+    {
+        static_cast<PANEL_SETUP_SEVERITIES*>( m_treebook->ResolvePage( m_severitiesPage ) )
+                ->ImportSettingsFrom( file.m_ErcSettings->m_ERCSeverities );
+    }
 
     if( importDlg.m_NetClassesOpt->GetValue() )
-        m_netclasses->ImportSettingsFrom( file.m_NetSettings );
+    {
+        static_cast<PANEL_SETUP_NETCLASSES*>( m_treebook->ResolvePage( m_netclassesPage ) )
+                ->ImportSettingsFrom( file.m_NetSettings );
+    }
 
     m_frame->GetSettingsManager()->UnloadProject( otherPrj, false );
 }
diff --git a/eeschema/dialogs/dialog_schematic_setup.h b/eeschema/dialogs/dialog_schematic_setup.h
index a65ae5d111..47b7a4154a 100644
--- a/eeschema/dialogs/dialog_schematic_setup.h
+++ b/eeschema/dialogs/dialog_schematic_setup.h
@@ -1,7 +1,7 @@
 /*
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
- * Copyright (C) 2020-2022 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2020-2023 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software: you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
@@ -45,16 +45,16 @@ protected:
     void onPageChanged( wxBookCtrlEvent& aEvent ) override;
     void onAuxiliaryAction( wxCommandEvent& aEvent ) override;
 
-    SCH_EDIT_FRAME*             m_frame;
+    SCH_EDIT_FRAME*           m_frame;
 
-    PANEL_SETUP_FORMATTING*     m_formatting;
-    PANEL_TEMPLATE_FIELDNAMES*  m_fieldNameTemplates;
-    PANEL_SETUP_PINMAP*         m_pinMap;
-    PANEL_SETUP_SEVERITIES*     m_severities;
-    PANEL_SETUP_NETCLASSES*     m_netclasses;
-    PANEL_SETUP_BUSES*          m_buses;
-    PANEL_TEXT_VARIABLES*       m_textVars;
-    std::shared_ptr<ERC_ITEM>   m_pinToPinError;
+    std::shared_ptr<ERC_ITEM> m_pinToPinError;
+
+    size_t                    m_formattingPage;
+    size_t                    m_fieldNameTemplatesPage;
+    size_t                    m_pinMapPage;
+    size_t                    m_busesPage;
+    size_t                    m_severitiesPage;
+    size_t                    m_netclassesPage;
 };
 
 
diff --git a/include/widgets/wx_treebook.h b/include/widgets/wx_treebook.h
index 7d353888eb..45c794e8f2 100644
--- a/include/widgets/wx_treebook.h
+++ b/include/widgets/wx_treebook.h
@@ -39,7 +39,7 @@ public:
     bool AddLazySubPage( std::function<wxWindow*( wxWindow* aParent )> aLazyCtor,
                          const wxString& text, bool bSelect = false, int imageId = NO_IMAGE );
 
-    wxWindow* ResolvePage( int aPage );
+    wxWindow* ResolvePage( size_t aPage );
 };
 
 
diff --git a/pcbnew/dialogs/dialog_board_setup.cpp b/pcbnew/dialogs/dialog_board_setup.cpp
index f7aaacc754..3e70972daf 100644
--- a/pcbnew/dialogs/dialog_board_setup.cpp
+++ b/pcbnew/dialogs/dialog_board_setup.cpp
@@ -38,7 +38,6 @@
 #include <settings/settings_manager.h>
 #include <widgets/resettable_panel.h>
 #include <widgets/wx_progress_reporters.h>
-#include <widgets/wx_treebook.h>
 #include <wildcards_and_files_ext.h>
 
 #include "dialog_board_setup.h"
@@ -102,7 +101,6 @@ DIALOG_BOARD_SETUP::DIALOG_BOARD_SETUP( PCB_EDIT_FRAME* aFrame ) :
                 return new PANEL_SETUP_FORMATTING( aParent, m_frame );
             }, _( "Formatting" ) );
 
-    m_textVarsPage = m_treebook->GetPageCount();
     m_treebook->AddLazySubPage(
             [this]( wxWindow* aParent ) -> wxWindow*
             {
@@ -129,13 +127,13 @@ DIALOG_BOARD_SETUP::DIALOG_BOARD_SETUP( PCB_EDIT_FRAME* aFrame ) :
     m_treebook->AddLazySubPage(
             [this]( wxWindow* aParent ) -> wxWindow*
             {
+                BOARD* board = m_frame->GetBoard();
                 return new PANEL_SETUP_NETCLASSES( aParent, m_frame,
                                                    m_frame->Prj().GetProjectFile().NetSettings(),
-                                                   m_frame->GetBoard()->GetNetClassAssignmentCandidates(),
+                                                   board->GetNetClassAssignmentCandidates(),
                                                    false );
             }, _( "Net Classes" ) );
 
-    m_rulesPage = m_treebook->GetPageCount();
     m_treebook->AddLazySubPage(
             [this]( wxWindow* aParent ) -> wxWindow*
             {
@@ -146,15 +144,18 @@ DIALOG_BOARD_SETUP::DIALOG_BOARD_SETUP( PCB_EDIT_FRAME* aFrame ) :
     m_treebook->AddLazySubPage(
             [this]( wxWindow* aParent ) -> wxWindow*
             {
+                BOARD* board = m_frame->GetBoard();
                 return new PANEL_SETUP_SEVERITIES( aParent, DRC_ITEM::GetItemsWithSeverities(),
-                                                   m_frame->GetBoard()->GetDesignSettings().m_DRCSeverities );
+                                                   board->GetDesignSettings().m_DRCSeverities );
             }, _( "Violation Severity" ) );
 
     for( size_t i = 0; i < m_treebook->GetPageCount(); ++i )
         m_treebook->ExpandNode( i );
 
-    m_treebook->SetMinSize( wxSize( -1, 580 ) );
-    m_treebook->SetInitialSize( wxSize( -1, 700 ) );
+    // This is unfortunate, but it's the cost of lazy-loading the panels
+    m_treebook->SetMinSize( wxSize( 980, 600 ) );
+    m_treebook->SetInitialSize( wxSize( 980, 600 ) );
+
     SetEvtHandlerEnabled( true );
 
     finishDialogSettings();
@@ -180,7 +181,7 @@ void DIALOG_BOARD_SETUP::onPageChanged( wxBookCtrlEvent& aEvent )
 {
     PAGED_DIALOG::onPageChanged( aEvent );
 
-    int page = aEvent.GetSelection();
+    size_t page = aEvent.GetSelection();
 
     // Ensure layer page always gets updated even if we aren't moving towards it
     if( m_currentPage == m_physicalStackupPage )
diff --git a/pcbnew/dialogs/dialog_board_setup.h b/pcbnew/dialogs/dialog_board_setup.h
index ab0829b6bf..c5621c4e6b 100644
--- a/pcbnew/dialogs/dialog_board_setup.h
+++ b/pcbnew/dialogs/dialog_board_setup.h
@@ -60,17 +60,15 @@ public:
     static std::mutex g_Mutex;      // Mutex to prevent multiple windows opening
 
 private:
-    int m_currentPage;              // the current page index
-    int m_textAndGraphicsPage;
-    int m_constraintsPage;
-    int m_formattingPage;
-    int m_physicalStackupPage;
-    int m_tracksAndViasPage;
-    int m_netclassesPage;
-    int m_maskAndPagePage;
-    int m_rulesPage;
-    int m_severitiesPage;
-    int m_textVarsPage;
+    size_t m_currentPage;              // the current page index
+    size_t m_textAndGraphicsPage;
+    size_t m_constraintsPage;
+    size_t m_formattingPage;
+    size_t m_physicalStackupPage;
+    size_t m_tracksAndViasPage;
+    size_t m_netclassesPage;
+    size_t m_maskAndPagePage;
+    size_t m_severitiesPage;
 };