So first off, I really like having a quest editor tool available. It looks like it works pretty good, too, though I've only fiddled around with it a little bit.
However, one thing I would like to see added are markers for heroes, as well as the monsters. Two reasons for this: one, I'd like to see quests that involve an NPC hero, either working with the heroes or against them. The second reason, and one that's not entirely related to the quest vault, is that I run a few play-by-post games of Descent, and having a nice mapmaking tool like this would come in very handy, as I could track monster and hero position very easily with this.