This emptying of editor, seems to only happen when a subtag is active in tag list of either split screen view panes. And then will also happen in regular view (not split view) when you switch back to Bear from other apps.
So when a top level tag is activated in tag list, everything seems to work fine and as expected
Sorry @trix180, I see that you have already found out about this issue in another thread – well this will serve as a confirmation then