I found this thread while I was looking for a way to manage tags, to use with the "folder structure to .json" thingy (I lost the relevant thread), after trying the
Kindle Collection Manager (this forum is an incredible maze of awesome stuff for a brand new user) and...
Well my point was that your plugin works perfectly and that I'm infinitely grateful for it
So I just wanted to say kudos and thanks so much for sharing your hard work with us!