Defraggler doesn't seem sum up fragmented directory-entries on the "file list" tab after an analysis. I almost always use that because a full defrag is a waste of time since it easily takes 10 times longer. Anyway, directories don't show up there, so it's not possible to defragment them the manual way.
It seems that directories get defragged only when doing a full defrag...
And since I have a few directories that are constantly being fed with thousands of (contiguous) files, I'd like to defrag them like I can with regular files...