Well, hmm… is it not? I just poked around at it, and I was able to get the folders to move where I wanted them, though only if I had the nearby folders in a ‘closed’ state. Not the most intuitive UX (their own on-page element tree allows for this by moving the mouse left/right to help indicate whether you’re trying to place the selection inside or beside a nearby container), but if the functionality is there, I’ll take it. :)