I didn't see any other issues related to drag+drop in source tree.
I used the "filter repositories" field in the repository browser to narrow the list to just a few repos that share a common element in their name (it wasn't a prefix so when unfiltered they were scattered apart from each other alphabetically). I then selected them and was expecting to be able to drag and drop them into a repository group that I had made but was not able to.
Can this use case be supported?