Why do all the extra SU window vanish on my Mac when I do this?

SketchUp
6

Yeah, I tried the other options too, All Desktops or None.

I also tried this

I found that unchecking

Preferences->Mission Control->Automatically rearrange spaces based on most recent use

also helped. I think SketchUp gets confused when the spaces are renumbered based on use!

as suggested in this topic.

Nothing I have tried so far has helped.