Hm well if we’re talking about the WK notion of radical then those are often just previous kanji you’ve learned. So any kanji that finds itself within another kanji could be a “radical”. But there are certainly even official radicals that WK doesn’t teach.
These are mostly just used for organization. Each character gets one radical which is often used to order things like character dictionaries. (Although sometimes characters get radicals just so that they can be put into a category) There are quite a lot here that WaniKani doesn’t teach, although many of them are variations on other radicals. But there is for example ⾲ “leek” which seems to be used in about 15 kanji. Although none of them are 常用, or even very common. I’m sure there are more that are on that list and even components not on that list that get used in places. The question I guess is if the only notable thing about a character is that it uses a funny shape, how worth is it to know about that character.
EDIT: There’s also 瓦 “tile”. Which is used in joyo kanji and is on the 214 list but isn’t taught by WK
A curious question. There are two things about WaniKani’s take on the kanji component “radicals” is that firstly, many of them are elementary enough that you could probably assemble anything if you use enough of them, and secondly, they’re often treated rather flexibly - i.e. close enough is good enough. So even for the kanji which are made up of parts that aren’t quite the same as WaniKani’s radicals, WaniKani would probably go “eh, close enough”.
For example, 臼 is not the same as 日, but WaniKani’s radical would probably be something like… “Oh, somebody dropped a mortar on the sun, and now it’s got a big crack in it”.
Or 繭 has an assemblage in the middle that’s “forehead” with “stick” in the middle, but WaniKani would probably go "eh, that’s close enough to ‘towel’ ".
WaniKani includes that one in the 瓶 kanji as “ten thousand” plus “drop” plus “ground”.
There are tens of thousands of Chinese characters out there, if you include all the rare and ancient characters things get really messy really quick. Where does a kanji like 龜 (traditional variant of 亀) fit for instance?
If you dig in there you’ll find some unfamiliar shapes. Consider something like 乘 which is a bit tricky to break down nicely using WK so-called radicals for instance.
But frankly the question is a bit moot, WK treats 綱 and 網 as identical radical assemblies for instance, and says that 垂 uses the 車 radical. It’s not systematic or based on any sort of proper decomposition of the characters.
Well, this Y in the middle is a new one. Maybe we gotta invent a new radical that’s just the letter Y (in the same way as “lion” is just the letter L).
In the meantime, I’ma say it’s “lid” + “sword” + “horns” + “stick” + a modified “clan” + a modified “moon”
(WaniKani regards the bottom section of the “simultaneous” radical as “moon”, so there’s precedent.)
I think RTK does a reasonable job here of trying to guide the student into the idea that they should make their own “component” mnemonics when they encounter new kanji that have clear subcomponents that didn’t turn up in the set RTK covers – there’s a set of kanji near the back for that purpose and some comments on how to approach it. But then RTK in general wants the student to do a lot more of the making up stories part themselves.
For me the approach is always to look for phonosemantic composition. Even when the components don’t really work I still find that it makes it easier to break the kanji in two chunks and remember them that way.
Of course not every kanji is a phonosemantic compound, but over 70% of all WK kanji are, and as you get above level 40 or so it’s usually 80 to 90% of kanji.