Yes, I have found bug #70479 a few days ago, too. For the rest of the
people on the list: it does not seem possible (or at least it would be
very difficult) to implement drag and drop of multiple items in tree
views. So for now, I am planning to implement dnd of single items only,
and the user will be able to copy multiple items using the right-click
menu. I hope this is OK, and let's hope the Gnome people fix this bug soon.