Can't split panels top to bottom... Rated 4 out of 5 stars
...Because neither my laptop touchpad nor my mouse has a middle button. I would hope that there is a method of forcing the application to do this some other way. This is the only reason I have given it a 9.This review is for a previous version of the add-on (0.8.6).
Ctrl and Shif clicks
Ctrl click the menuitem for horizontal slpit on bottom of window or Shift click for vertical slpit on right side of window. They correspond to middle or right clicks.