I located something called the RK1 supplement pdf online. It’s not something that you take. It’s something that you read—when you’re reading Japanese.
“In spring of 2010, the Japanese Ministry of Education, Culture, Sports, Science, and Technology announced the addition of 196 kanji to the 1,945 characters of the list of general-use kanji approved in 1981.”
After that, James Heisig went to work to update his book, Reading the Kanji. He added 5 more chapters to bring the total number up to 62. That’s what I’m working through now, to expand what I’ve done in developing my kanji alphabetizer.