It's something I haven't tried because I can already predict the outcome. I'd get into for a few weeks, I'd put a bunch of stuff in there, but I wouldn't be able to break the muscle memory of just using Google/DDG when I need to know something. Then I'd inevitably give up.
Respect to those who do it and it works for them though.
Same; I installed SnippetsLab a while ago and put some stuff in it, it's neat, but I rarely find myself actually looking up stuff in there again. It's got stuff like the odd Bash line for advanced Git stuff (like looking up certain statistics), but that's rarely used.
That said, if you put it up on a website and add a short blurb, search engines can come index it, and others may be able to find and use it.
Sometimes my search ends up on a Github Gist, which will often have a bit of discussion in the comments as well.