Same; I've been using various note taking approaches over the years, but my "problem" is that I rarely actually have to go back to a note, they are usually only relevant for one task like e.g. writing a blog post or implementing a feature.

So while I'd like to retain my knowledge and research somewhere, at the same time I don't actually use it???

But some writing I've done that will be relevant in the next years is writing ADR's (Architecture Decision Records) in my application about technology and architecture choices I've made, so I can look them up later, use it to train new people, and have a basis to challenge a decision on as well. That's more practical for my personal situation.

But maybe one day I'll be doing something more academic and will need a way to collate research and the like.