You will need to install a user script manager extension to install this script.
Adds User Synonyms to the lessons page. Adds User Synonyms and Notes to unlearned item pages.
This is an update of the version that was originally provided by @kobayashi (Takuya Kobayashi) and has been adapted to work with a newer version of WaniKani. The original "WaniKani Lesson User Synonyms" in version 0.1.2 has been broken since November 2017.