This concern is a bit overblown here. There are 23 KDE patches at the moment, across multiple packages. kwin itself has 5, plasma-desktop has 4. Each one has an

This concern is a bit overblown here. There are 23 KDE patches at the moment, across multiple packages. kwin itself has 5, plasma-desktop has 4. Each one has an extremely limited scope - mostly one line changes related to paths rather than visible functionality. If you have a specific issue under nixos, it's going to be fairly easy to see if it's very unlikely to be caused by custom patches.