It’s possible at the application level for Qt stuff at least, iirc you just pass a window arg to enable transparency. If you mean from like a user settings perspective, idk sorry 😂

Technically I’m sure it’s possible, I’ve seen programs that have a kind of frosted see-through look. But that’s something the program has to implement.

Could you grab the desktop background image, then do some trickery rendering the image using the window position to pan and crop it?

Sovled: Users here suggested https://github.com/taj-ny/kwin-effects-forceblur which works wonderfully, even with video wallpapers!