If the "Show directory title at top" checkbox is disabled there is no visible area on the STM GUI to drag it with.
Could the blank space where the Function keys are located also be a "draggable" area?
It would be convenient to be able to drag it both from the top or the bottom.

Edit:
I just realised there is a small amount of space at the top of STM when there is no Title bar where it can be dragged but it is very hard to find and select so maybe the draggable area at the top could be made slightly bigger if needed and highlighted but only on a mouseover?

This would work even if the Title bar and Function key bar are hidden.