How do the blue handles function?

The blue handles allow you to split edges to add more corners. Simply drag and drop the blue handle to add a corner. If you just want to split a wall into different sections without adding a new corner, you can drag and drop the blue handle in line with the existing wall. This can be used to  add complex rooms to your floor plan, for example L-shaped rooms. 

For more help on this topic, see our guide on Creating Rooms.