Is there documentation on what subset of XUL is supported?
I'll see if I can track this down. Until then, http://www.adobe.com/devnet/flash/articles/invisible_button.html (although a bit old) might have some useful information.
Senior Content and Community Manager
Adobe Systems Incorporated
With some help from the team, we were able to find an archived page that has some of this: http://webcache.googleusercontent.com/search?q=cache:http://photoshop-flash-coreldraw-seo- help.com/adobe-flash-help-tutorials/control-tag-summary-of-xml-to-ui-in-flash.html.
For your convenience, I'm pasting an image of the list:
Thanks, that's extremely helpful!