Hmm.
The button will return in another update, our board software just released a major version and we've been preparing for that update. I removed the stuff that powered said button. The new version of xF actually includes a new way of making buttons for the editor. We plan to update sometime...
Its mostly tied to the tabs bbcode, it was made safer and unexpliotable by @Lyro
We are looking to see what can be done. Nothing else should have changed.
Woot.
Firefox has been stepping up their game and I'm super stoked for their new web engine. I want to see if we can collaborate later and create an RpN Suite for Chrome/FF. Been working on browser themes for both :D!