I've added both decensum and divintion to her confrimed power list. Both of them satisfy the standards for confirmed status.
Transmutation is just no though, sorry. There is no way to no for sure she has disappeared from one location and appeared in another. It could be that she wonders to these locations via conventional means. We just don't know for certain.
Decensum is the ability to descend into the depths of the hell, misty has done this. Editors took that power of her list because she couldn't return, but I believe the power is simply to be able to get there. Whether you return is at the witch's discretion.
Now that I think about it, I agree with Misty's Descensum, since Myrtle said that going down will be easy for girls with their talent; that leaves for interpretation the fact that a younger or inexperienced witch would say the incantation but wouldn't be able to travel down below (just speculating). That's what I didn't like about Coven, some things weren't explained.
Divination, the one we debated harder for, I agree with it and moreso. Misty was so perceptional, and not the kind of humane intuitive kinda way, but the kind a witch has :).
Transmutation, hmmm, while I always thought she possessed, the rules of this wiki have to respected. If it was up to only me I would list it, because just like Divination she showed it in multiple times, I just think we sometimes overlook things because writers/editors were not giving all the powers away. Why do you think they fully explained which The Seven Wonders were till the second to last episode? They were keeping it to themselves, which for me was a huge mistake (to leave it till almost the finale). I think we should list it once someone explains it better than us or when someone interviews Ryan Murphy xD.