Any idea why drag and drop would not be working? I have quick download/upload enabled, and uploads work when I initiate them using the keyboard shortcut and select the file manually. Drag and drop works for me in other apps (see video below).
Could you please try open a local shell in Core Shell and try drag and drop again? It seems there is a glitch in Core Shell's DnD support.
It does work in a local shell for me.