- https://webpg.org/ -- extension in question
I realize it's best practice to not install any Addons/extensions on Tor at all but I'm trying to make email based encryption easy and practical enough for a relative technical novice to use. I am hoping this allow them one click encryption of gmail over Tor as it does for regular firefox (so long as they had gpg installed already).
I'm fairly sure you can't register and use a gmail account through tor without phone verification, which means that there would have been a trail, and that means you're essentially already de-anonymized.