I'm starting to have a mental picture of the code structure for v2.0, which would include a suggestion I got from a guy on GitHub to allow for each Editor to be detached as its own window.This sounds great. And regarding other improvements, you of course decide what is best, possible and realistic to do.
Not sure if you have multiple monitors but I thought this might help in the case you've been describing about seeing the changes in the Tilemap when editing the Tileset/Selection.
It is however a huge change in the code and it would take a while before I would have something that compiles and runs, so don't know when I'll get around to start working on it.