First of all, I would like to say that this is an unrealistically cool experience - the new multi-window mode feels very good and promising so far! Hats off to the whole team for all their hard work!
After talking to colleagues and using it, the first thing that came to mind was a “Minimise” button on such windows. I’m not quite sure how it would work, but do you think it would be useful? (I think it would be absolutely amazing if we could also have this functionality in the main editor window)