diff --git a/WineFix/Patches/SubToolColumnsPatch.cs b/WineFix/Patches/SubToolColumnsPatch.cs
new file mode 100644
index 0000000..959cbfb
--- /dev/null
+++ b/WineFix/Patches/SubToolColumnsPatch.cs
@@ -0,0 +1,95 @@
+using System;
+using System.Collections;
+using System.Linq;
+using System.Reflection;
+using System.Windows;
+using HarmonyLib;
+using AffinityPluginLoader.Core;
+
+namespace WineFix.Patches
+{
+    /// <summary>
+    /// Keeps the sub-tool panel's column count across a studio switch.
+    ///
+    /// The sub-tool panel is a ToolTray like the main tool pane. SubToolPanel.ToggleVisibility
+    /// gives it two columns when the current tool has more than ten sub-tools (the shape tools)
+    /// and one otherwise, and runs whenever the tool changes. A studio switch also raises
+    /// CurrentWorkspaceChanged, and every ToolTray handles that by setting Columns to
+    /// ToolSettings.ToolPaneColumns -- the main tool pane's setting. With a one-column tool pane
+    /// the shape tools came back as a single column running the height of the window, until
+    /// the next tool change put two columns back.
+    ///
+    /// After that handler, the sub-tool panel's tray gets its own rule back. The main tool pane
+    /// is left alone.
+    /// </summary>
+    public static class SubToolColumnsPatch
+    {
+        private static PropertyInfo _toolhostProperty;
+        private static PropertyInfo _subToolRootProperty;
+        private static PropertyInfo _columnsProperty;
+        private static PropertyInfo _currentToolProperty;
+
+        public static void ApplyPatches(Harmony harmony)
+        {
+            Logger.Info("Applying SubToolColumns patch...");
+
+            var serifAssembly = AppDomain.CurrentDomain.GetAssemblies()
+                .FirstOrDefault(a => a.GetName().Name == "Serif.Affinity");
+            if (serifAssembly == null)
+            {
+                Logger.Error("Serif.Affinity assembly not found");
+                return;
+            }
+
+            var trayType = serifAssembly.GetType("Serif.Affinity.UI.Controls.Tools.ToolTray");
+            var hostType = serifAssembly.GetType("Serif.Affinity.UI.Controls.Tools.ToolHost");
+            var windowType = serifAssembly.GetType("Serif.Affinity.UI.AffinityWindow");
+            var handler = trayType == null ? null
+                : AccessTools.Method(trayType, "WorkspaceService_CurrentWorkspaceChanged");
+
+            _toolhostProperty = windowType == null ? null : AccessTools.Property(windowType, "Toolhost");
+            _subToolRootProperty = hostType == null ? null : AccessTools.Property(hostType, "SubToolRoot");
+            _columnsProperty = trayType == null ? null : AccessTools.Property(trayType, "Columns");
+            _currentToolProperty = trayType == null ? null : AccessTools.Property(trayType, "CurrentTool");
+
+            if (handler == null || _toolhostProperty == null || _subToolRootProperty == null
+                || _columnsProperty == null || _currentToolProperty == null)
+            {
+                Logger.Error("ToolTray/ToolHost members not found; sub-tool columns left as they are");
+                return;
+            }
+
+            harmony.Patch(handler, postfix: new HarmonyMethod(typeof(SubToolColumnsPatch), nameof(CurrentWorkspaceChanged_Postfix)));
+            Logger.Info("Patched ToolTray.WorkspaceService_CurrentWorkspaceChanged");
+        }
+
+        public static void CurrentWorkspaceChanged_Postfix(object __instance)
+        {
+            try
+            {
+                var window = Application.Current?.MainWindow;
+                if (window == null || !_toolhostProperty.DeclaringType.IsInstanceOfType(window))
+                    return;
+                var toolhost = _toolhostProperty.GetValue(window);
+                if (toolhost == null || !ReferenceEquals(_subToolRootProperty.GetValue(toolhost), __instance))
+                    return;
+
+                // SubToolPanel.ToggleVisibility's rule.
+                var tool = _currentToolProperty.GetValue(__instance);
+                if (tool == null)
+                    return;
+                var children = AccessTools.Property(tool.GetType(), "Children")?.GetValue(tool) as ICollection;
+                if (children == null)
+                    return;
+                object columns = children.Count > 10 ? 2 : 1;
+                if (_columnsProperty.PropertyType == typeof(int?))
+                    columns = (int?)(int)columns;
+                _columnsProperty.SetValue(__instance, columns);
+            }
+            catch (Exception ex)
+            {
+                Logger.Error("SubToolColumns: " + ex.Message);
+            }
+        }
+    }
+}
diff --git a/WineFix/WineFixPlugin.cs b/WineFix/WineFixPlugin.cs
index d05ea2c..cf73a77 100644
--- a/WineFix/WineFixPlugin.cs
+++ b/WineFix/WineFixPlugin.cs
@@ -22,6 +22,7 @@ public class WineFixPlugin : AffinityPlugin
         public const string SettingWidenStubFix = "widen_stub_fix";
         public const string SettingBezierSplitGuard = "bezier_split_guard";
         public const string SettingCommandLineFileOpen = "command_line_file_open";
+        public const string SettingSubToolColumns = "sub_tool_columns_fix";
 
         public override PluginSettingsDefinition DefineSettings()
         {
@@ -69,6 +70,10 @@ public override PluginSettingsDefinition DefineSettings()
                     defaultValue: true,
                     restartRequired: true,
                     description: "Fix opening files from the command line or desktop file manager.")
+                .AddBool(SettingSubToolColumns, "Sub-tool panel: Keep its columns across studio switches",
+                    defaultValue: true,
+                    restartRequired: true,
+                    description: "A studio switch gives the sub-tool panel the main tool pane's column count, so with a one-column tool pane the shape tools come back as one column running the height of the window until the next tool change. Put back the sub-tool panel's own rule (two columns for more than ten sub-tools) after a studio switch.")
                 .AddSection("Crash Fixes")
                 .AddBool(SettingForceSyncFontEnum, "Force synchronous font enumeration",
                     defaultValue: true,
@@ -111,6 +116,16 @@ public override void OnPatch(Harmony harmony, IPluginContext context)
             context.Patch("MainWindowLoaded fix",
                 h => Patches.MainWindowLoadedPatch.ApplyPatches(h));
 
+            if (context.Settings.GetEffectiveValue<bool>(SettingSubToolColumns))
+            {
+                context.Patch("SubToolColumns fix",
+                    h => Patches.SubToolColumnsPatch.ApplyPatches(h));
+            }
+            else
+            {
+                Logger.Info("Skipping SubToolColumns fix (setting: disabled)");
+            }
+
             if (context.Settings.GetEffectiveValue<bool>(SettingForceSyncFontEnum))
             {
                 context.Patch("FontEnumeration fix",
diff --git a/docs/winefix/configuration.md b/docs/winefix/configuration.md
index de2a45a..22bf894 100644
--- a/docs/winefix/configuration.md
+++ b/docs/winefix/configuration.md
@@ -21,6 +21,7 @@ WineFix uses plugin ID `winefix`. Settings are stored in `apl/config/winefix.tom
 | `color_picker_sampling_mode` | enum | `native` | No | Controls how the color picker samples color values. See [Sampling Modes](index.md#color-picker-sampling-modes). |
 | `canva_sign_in_helper` | bool | `true` | Yes | Patch the Canva sign-in dialog to include a helper textbox and instructions to complete sign-in without a protocol URL handler. |
 | `command_line_file_open` | bool | `true` | Yes | Fix opening files from the command line or desktop file manager. Bypasses Affinity's broken `ProcessCommandLineArguments` which references a WinRT type missing in Wine. |
+| `sub_tool_columns_fix` | bool | `true` | Yes | Keep the sub-tool panel's own column count (two for more than ten sub-tools) after a studio switch, which otherwise gives it the main tool pane's. |
 
 #### `color_picker_magnifier_fix`