Option to intentionally delay levelling-up to avoid getting overwhelmed

Just to weigh in on this with a strategy I haven’t seen explicitly mentioned above, although it resembles that outlined by @slerched:

I have overcome the “too many lessons” issue by always having lessons ready, and by strictly limiting the number of lessons I do per day to a sustainable amount. I use the lesson filter script to reduce the number of available items to something like 4 radicals/kanji, and 10 vocab items, mirroring approximately the ratio of total rad/kan vs voc items per level. I never do more than that. As a result, my review load is very balanced, both in terms of total numbers, and in terms of item types - there’s always a good mix of a few items requiring “pure memorization”, and a bunch of vocab reinforcing already learned readings/meanings.

Finally, if for some reason I did run out of lessons (towards the end of a level, if the last few kanji didn’t stick), that’s when I start to panic. Keeping that rad/kan vs voc balance can be a little tricky at first, because the control surface, if you will - i.e., the daily lesson batch - is relatively small, and the system has a huge amount of inertia. I guess steering your Wanikani workload is more like ships than like airplanes in that way…

Anyhow, fly safe and don’t panic!