Very useful, I am trying to make a metroidvania right now, and while I had already drawn it out I think this helps me really think about how its going to flow instead of just day dreaming about it. Some ideas would be a way to pin a room in place so that its not constantly wiggling, a way to color rooms and lines that lead to rooms, the ability to drag and drop the rooms in the tool box in order to rearrange them, a way to show that there is an ability, item, or event in a room and tell the difference between them.
I am still going to use this and thanks its very useful.