the top menu options to import, export, go back to the main menu, etc, are gone from the top in full screen mode (though if I bring the pointer to pop up the top hotbar(?) I can see the options)
Hi!
It’s not a bug, they are all moved to the macos menu intentionally 
The back button is in the title bar now However I see it’s missing for you, which OS version do you use? It should be like this:
In this release, you will see many changes, and some visual “bugs”, which are still work in progress, and will be redesigned, removed or otherwise changed in the coming builds.
Cheers