I just learned about compose (desktop) and am now wondering if it is somehow possible to do some 3d rendering inside the application?

You might want to check out: https://github.com/google/filament I know @romainguy had a sample app (albiet old / out oof date at this point) which was using both Compose and Filament on Android: https://github.com/romainguy/sample-materials-shop He might have a better idea of what it would take to integrate Filament into a Compose/Swing desktop app, but afaik it should be possible.

Filament has support for AWT/Swing indeed

Oh thats great, thank you very much