When I was working on the expert for TMultiLang, I needed to display a menu in the expert's "main" form.
Now this form was created with TForm1.Create() and therefore not an application's main window.
This means:
Although the menu is displayed in design mode properly, at runtime it will not appear.
Even manually assigning the menu with Menu := MainMenu will not help.
Workaround:
Use the API function SetMenu in the FormCreate handler as shown below:
procedure TForm1.FormCreate(Sender: TObject);
var
h : integer;
begin
h := ClientHeight;
SetMenu (Handle, MainMenu1.Handle);
ClientHeight := h;
end;