I took some time to rework my changes a bit to fit in with the Wanikani style and ended up basically entirely overhauling the script so I posted it to GreasyFork and gave it its own thread.
This is what my new version looks like:
If you want to get back Wanikani’s new item type breakdowns, you can turn off replacing the radical/kanji/vocab count:
If you have more than 100 items in Apprentice III, or more than 1000 in Apprentice II or Apprentice IV, the items will jump around a little bit on hover when you display the leeches as there isn’t quite enough space, but otherwise it looks nicer.