Created attachment 150777 [details]
Gif illustration of "snap assist" feature

SUMMARY
Windows has a nice feature, which shows thumbnails of other windows when user snaps window to the one of the screen halves. It helps to immediately select next window to be placed near the first one, and it improves productivity a lot for mouse-oriented users. For Gnome, there is Tiling Assistant extension (https://github.com/Leleat/Tiling-Assistant) which provides similar functionality – but there's none for KDE, seemingly because Kwin scripting limitations do not allow to fully recreate such a feature. 

Therefore, I think it makes sense to request such a feature to be implemented in the system natively – especially in the light of other feature from Windows, "custom snap zones", currently being in the work (https://invent.kde.org/plasma/kwin/-/merge_requests/2560).