ah yes maybe drag'n'drop is not working I have no idea tbh but I don't remember it working reliably in virtualbox and shared folders always worked better in my limited experience.

Shared folders does indeed seem like a weak point for kvm/virt-manager. There's the virtioFS but this is a pretty recent addition that was also recently pretty buggy on Windows.

I'm not even sure what your alternatives were for this before now, I guess everyone was just using samba.