The things mentioned in your Google doc sound pretty good.
But something I was expecting for some reason when I first tried it out was that when you created a box that represented a scene, I thought the scene would be generated automatically with the size and everything. It doesn't matter how the scenes link together in-game, people will come up with their own methods.
Also, adding lines, dots, icons, etc would be rather handy.
What you have here is an incredibly simple and useful tool that it seems like so many people are already using. I for one, would love to see at least one more update.
Thanks for listening, and thanks for making the extension.