I don’t have any overscroll if no content is outside of the main screen.
Even if it is a tiny bit outside of the screen, it will do overscroll. Then if you avoid it, you won’t have overscroll.
That doesn’t stop you using smaller windows inside of the main one that has content bigger than the frame of the panel, and will do scroll, quite nicely (as long this is intentional). Simply is better to avoid more than one element doing scroll in the same point of the screen or will not know what scroll has priority.
There is a scroll locking in the panel, that works. But it’s not available in the root or with tabs. I hope we are talking about the same thing.
In any case would be nice to have a way to control the scroll in all parts besides panels (root, tabs etc) as that would avoid devices with different aspect ratio doing scroll when something is a bit outside.