Any time I think of something cool, see something cool, whatever - I add it / paste it into a long running note I have labeled "Cool stuff." Whenever I'm bored, I just read through it and usually find something I didn't have time to dig into more thoroughly before. Or, if I'm working on something and looking for something I noted earlier, again, just search for it in that note. The note also syncs automatically between my phone and computer, so requires zero mental bandwidth on my end for setup etc.
Can't understate enough how valuable this becomes over time, specific to the individual writing it. If I shared my note, it would probably be completely useless to the rest of humanity, but for me, it is a productivity 100x.
edit: typo