I've used personal wikis and knowledge bases for myself and they work okay. vimwiki has been useful for me.

I find that I do some pretty cool stuff and then totally forget how I did it a year or 5 years later, mostly with coding. The open source projects I documented and explained are things I myself google to help me set them up in the future, so a way of codifying my knowledge has been to try to write about it and put that in public.

I set up development environments for myself a lot, so I wrote an article about how I do it https://modfoss.com/creating-my-development-environment.html and then put the code on GitHub as well https://github.com/symkat/modfoss_devel So if I don't do it for a while, I'll have a starting point and me-from-the-past explaining what I did and why.