Patch 1.3.3 allows selecting multiple boundaries and combining them into one. The combination is a rectangle based on their bounding boxes. To access this you need to hold the Ctrl key down and left mouse button click on each boundary to add, then let go of the Ctrl key and right click the desktop
. You will now be given the option of Merging and Keeping the original boundaries or Merging and Deleting the original boundaries.
When selecting the boundaries they will blink. The blinking should stop when you take an action or you do another mouse interaction (left or right click) or hit Esc.