Editor Library
The Editor Library comprises, well, a whole lot of stuff!
There's no exhaustive explanation or API reference for this part of TilePlus. This one also advises you that Molag Bal will visit you if you mess around with this code. Seriously, there's no need although there's a lot of clues for those who like editor code.
Painter is a Painting / Editing tool with separate documentation for you to read. It’s UI-Elements based and does away with the concept of brushes completely.