Greasy Fork is available in English.
Adds type, genres and other info to entries tags. Can also delete all current tags.
< Feedback op MyAnimeList (MAL) Tags Updater
I'm on FF Quantum as well, and the script works perfectly fine. Try using Tampermonkey or Violentmonkey. I'm not sure if Greasemonkey is stable on FF Quantum already.
Tried installing Tampermonkey and it works! Thank you, akarin!
Firefox 57
Looks like the script doesn't work in FF Quantum. Fix it please.