diff --git a/examples/anchordocking/design/registeranchordocking.pas b/examples/anchordocking/design/registeranchordocking.pas
index 4828d6bbcb..0864b51191 100644
--- a/examples/anchordocking/design/registeranchordocking.pas
+++ b/examples/anchordocking/design/registeranchordocking.pas
@@ -64,6 +64,7 @@ type
     destructor Destroy; override;
     procedure MakeIDEWindowDockSite(AForm: TCustomForm); override;
     procedure MakeIDEWindowDockable(AControl: TWinControl); override;
+    function AddableInWindowMenu(AForm: TCustomForm): boolean; override;
     function GetDefaultLayoutFilename: string;
     procedure LoadDefaultLayout;
     procedure LoadUserLayout;
@@ -175,6 +176,14 @@ begin
   DockMaster.MakeDockable(AControl,false);
 end;
 
+function TIDEAnchorDockMaster.AddableInWindowMenu(AForm: TCustomForm): boolean;
+begin
+  Result:=false;
+  if AForm is TAnchorDockHostSite then exit;
+  if (DockMaster.FindControl(AForm.Name)=nil) and (AForm.Parent<>nil) then exit;
+  Result:=true;
+end;
+
 function TIDEAnchorDockMaster.GetDefaultLayoutFilename: string;
 begin
   Result:=AppendPathDelim(LazarusIDE.GetPrimaryConfigPath)+DefaultConfigFileName;
diff --git a/ide/mainbase.pas b/ide/mainbase.pas
index bcbeae166b..b574d7a1e3 100644
--- a/ide/mainbase.pas
+++ b/ide/mainbase.pas
@@ -61,7 +61,7 @@ uses
   CodeToolManager, CodeCache, AVL_Tree, SynEditKeyCmds,
   // IDEIntf
   LazConf, LazarusIDEStrConsts, SrcEditorIntf, LazIDEIntf, MenuIntf,
-  IDECommands, IDEMsgIntf,
+  IDECommands, IDEMsgIntf, IDEWindowIntf,
   // IDE
   ProjectDefs, Project, PublishModule, BuildLazDialog, Compiler,
   ComponentReg, OutputFilter,
@@ -209,8 +209,7 @@ begin
   while (i>=0) do begin
     if Screen.CustomForms[i].Caption=(Sender as TIDEMenuCommand).Caption then
     begin
-      Screen.CustomForms[i].Show;
-      Screen.CustomForms[i].BringToFront;
+      IDEWindowCreators.ShowForm(Screen.CustomForms[i],true);
       break;
     end;
     dec(i);
@@ -1048,10 +1047,17 @@ begin
   // add special IDE windows
   for i:=0 to Screen.FormCount-1 do begin
     AForm:=Screen.Forms[i];
-    if (AForm.Parent=nil) and (AForm<>MainIDEBar) and (AForm<>SplashForm)
-    and (AForm.Designer=nil) and (AForm.Visible)
-    and (WindowsList.IndexOf(AForm)<0) then
-      WindowsList.Add(AForm);
+    //debugln(['TMainIDEBase.UpdateWindowMenu ',DbgSName(AForm),' Vis=',AForm.IsVisible,' Des=',DbgSName(AForm.Designer)]);
+    if (not AForm.IsVisible) or (AForm=MainIDEBar) or (AForm=SplashForm)
+    or (AForm.Designer<>nil) or (WindowsList.IndexOf(AForm)>=0) then
+      continue;
+    if IDEDockMaster<>nil then
+    begin
+      if not IDEDockMaster.AddableInWindowMenu(AForm) then continue;
+    end else begin
+      if AForm.Parent<>nil then continue;
+    end;
+    WindowsList.Add(AForm);
   end;
   // add designer forms and datamodule forms
   for i:=0 to Screen.FormCount-1 do begin
diff --git a/ideintf/idewindowintf.pas b/ideintf/idewindowintf.pas
index 6eca89ae9c..10d3d2d646 100644
--- a/ideintf/idewindowintf.pas
+++ b/ideintf/idewindowintf.pas
@@ -343,6 +343,7 @@ type
     procedure MakeIDEWindowDockable(AControl: TWinControl); virtual; abstract; // make AControl dockable, it can be docked and other dockable windows can be docked to it, this does not make it visible
     procedure MakeIDEWindowDockSite(AForm: TCustomForm); virtual; abstract; // make AForm a dock site, AForm can not be docked, its Parent must be kept nil, this does not make it visible
     procedure ShowForm(AForm: TCustomForm; BringToFront: boolean); virtual; abstract; // make a form visible, set BringToFront=true if form should be shown on active screen and on front of other windows, normally this focus the form
+    function AddableInWindowMenu(AForm: TCustomForm): boolean; virtual;
     procedure CloseAll; virtual; // close all forms, called after IDE has saved all and shuts down
   end;
 
@@ -1479,6 +1480,11 @@ end;
 
 { TIDEDockMaster }
 
+function TIDEDockMaster.AddableInWindowMenu(AForm: TCustomForm): boolean;
+begin
+  Result:=true;
+end;
+
 procedure TIDEDockMaster.CloseAll;
 begin
   CloseAllForms;