Preferences - Menubar

I was editing the Preferences to change the appearance of the Main Menu, when I decided to explore the options as to which other menus I could change.

I spotted that I could edit the "Menubar", except I did not know what the "Menubar" is. So I added an icon which I knew I didn't have anywhere else, applied, then exited out. But I still could not see it anywhere!

Can anyone tell me where I find this "Menubar"

Thanks

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