Starting with 2.5.0b1, drag & drop of directories from the file tree area to the cluster area seems to be broken. The first 2-3 or max 4 directories work fine, but after that the cluster area refuses to react to the "drop" action (ie. releasing the mouse button), although the cursor shows the little "+" to idicate that it's currently hovering over a "drop" target.
I can still drag & drop files to the cluster area, but I have to expand the directory in the file tree area, select all the files in the directory, and then drag & drop them to the cluster area.
Going back to 2.4.4 immediately brings back the usual behaviour, where I can drag & drop as many directories as I want.