Not sure if this is the right place to ask this since this is more of an “abstract” question about grammar, but it’s something that I was thinking about recently. I know that 五段 verbs are an open class (to an extent), with stuff like ググる and サボる having been created relatively recently, the former especially, but I haven’t seen anything similar with 一段 verbs.
In case you don’t know what open and closed classes are, they’re terms that refer to the ability of word classes in a language (nouns, verbs, adjectives, stuff like that) to accept new words. Open classes are able to accept new words, closed classes aren’t. An example of an open class in English would be verbs: new verbs are being invented/coined all the time in English, so English verbs are an open class. On the other hand, prepositions are very much a closed class. There are a finite number of prepositions and there aren’t any new ones popping up anywhere (from what I can tell at least).
If you know of any new 一段 verbs, let me know! I’d be very interested to see them.