I have a couple of separate windows and tried for a long time to get them all a separate Menubar, but this is impossible, too buggy, or very complicated and not straight forward like simply creating a Menubar and then assigning it in the Inspector. So now I just want to have the windows with no Menubar at all, but even that seems to be not possible. Any suggestions on how to work with them? I must misunderstand the whole concept.
Like always, after posting a question, one finds the answer; it must be some kind of universal law…:
Remove any old MenuBars and Menu Handlers you tried to add before to those windows to avoid confusing.
Add a new MenuBar to the window you want it t appear in:
Assign it to the window you want it to appear in the Inspector.
Start adding Menu items and Menu Handlers to that window as usual.
It worked for me when I started to add the items from scratch and not copy and paste from the App.menuBar; that seems to create some kind of Instance, not a real new one.