I managed to get this working. For anyone else who gets stuck on this, the text before the dot should be your product module name found in the build settings. The sample code uses 'Editor' which is kinda confusing in the context of file types/documents since 'Editor' is also a role. The thing that was throwing me was that my app name has a space but evidently the UIDocumentClass value cannot have spaces. I wish this stuff was documented somewhere. Maybe ModuleName.Value is a common pattern but I don't see it any other plist entries.

For anyone else stuck with this issue, it can be solved with UINavigationBarDelegate like so: @available(macCatalyst 16.0, *)     func navigationBarNSToolbarSection(_ navigationBar: UINavigationBar) -> UINavigationBar.NSToolbarSection {         return .content     }

You are correct, I'm building the main menu in my app delegate. At present I'm only overriding validate() in the app delegate. You must implement your commands and the validation overrides on your presented view controller, When I implement the overrides in the presented view controller the new menu item isn't added to the main menu. or on the app delegate, for them to continue working during form sheet presentations. Isn't this what I'm doing already? A fundamental difference between the fullscreen and page sheet presentations on Catalyst is that page sheet presentations get their own scenes and UIWindow instances, so the responder chain do not lead back to the presenter’s window. Instead, the responder chain goes up to the form sheet’s scene, then to your app instance, and your app delegate (if it is a UIResponder). What is the implication of this if my menu is built in the app delegate? The new window with its own responder chain should still reach the app delegate, or am I misunderstanding?

Same issue, again on 2018 11" iPad Pro. Soon as I unlock the device springboard seems to crash. This loops a fews times then the entire screen turns pink and the iPad turns off. Also did DFU restore to 14.6.

Same issue, again on 2018 11" iPad Pro. Soon as I unlock the device springboard seems to crash. This loops a fews times then the entire screen turns pink and the iPad turns off. Also did DFU restore to 14.6.