Greasy Fork is available in English.
Show which JLPT level the kanji or vocabulary word is in (if at all) according to Jonathan Waller‘s JLPT Resources page http://www.tanos.co.uk/jlpt/. The code is based on dtwigs "WaniKani Common Vocab Indicator" script. This code is at https://github.com/NicoleRauch/WaniKaniJLPT
I love this script, but does not appear to be working after the recent update.