I tried the latest release and still the same problem. I'm starting to suspect Apple's ios/ipados framework in MacOs. A subwindow/menu not showing must have something to do with the framework translation in MacOs. Some kind of limitation? Running Monterey btw.
I'm not dead in the water as I can use the Mac version or the iPad for smaller work. I'm currently working on a big 10mx2m wall project with ASP. ASP workflow is excellent, Photoshop and Affinity Photo can't compete at all. Trust me I have tried.

Made a video of my problems.

Yes.
I'll test it when I come home from work.

I had no time to make the recording.

Picking colors for the different lines in the perspective grid settings doesn't work. Nothing happens when trying to click the color square. It's the same problem with other settings when I try to choose colors. The main color wheel is working though. The perspective grid don't show except for the horizon. Maybe a flaw in Apple's translation layer of the IOS/iPadOs API?

Yeah, it would be really cool!
But using a dedicated video editor is probably the best way to go.
Luma Fusion is cheap and easy to use as an example.

Users with 2,4, and 6 GB of RAM will probably end up using virtual memory. And everything slows down to a crawl.
Original animation drawings, animation cache and then adding audio files to the mix will be problematic to fit into physical memory.
An iPad with 8-16GB ram will probably work. But personally, I can't afford one and I guess it's not only me. 

Solved. Running a Linux server for storage I had to add this to the samba configuration.

By section global at the end add: fruit:nfs_aces = no
By section share add: vfs objects = catia fruit streams_xattr

I had the same problem with Apple devices smb shares too. I hope newer devices are patched.

Created with the latest versions for Desktop and iPad.