Something I was taught in college helps me a lot. Identify the problem, then think about the problem you wish to solve, then create a word cloud about what you know. Research the topic, and expand the word cloud. Then, when you have some knowledge, attempt to produce drafts of what could solve the problem. See what can be improved, and iterate. In my case, this was for graphic design, but it's helped me in illustration when I'm fresh out of ideas, and in creative writing (as a DM). I've realized it was sort of like design thinking mixed with lateral thinking. It's about tackling problems through a methodological creative process, to eliminate bias and inform decisions as much as possible.

For a stretch of time after college I had issues with creative solutions even with that method, however. After finally being checked out by a psychiatrist, it turns out I was depressed and anxious to high heaven. After I started taking medications and doing what my psychologist taught me, not only did the classical symptoms of GAD, depression and adhd ameliorate, I started to feel creative again.

As for the sticky note thing you mentioned, I tried that and ended up having piles of sticky notes that I couldn't easily recall. I started using google keep at first, and now use Notion instead. Wish there was a FOSS detective board style app or something to map my ideas and write down simple notes. Would help me organize my mind a lot.

Edit: also, for reference, I've scored high on self-diagnosis exams on embrace autism, but wasn't diagnosed with it. Idk if my psychologist is up to date with the current science, because the reason she gave me for not diagnosing me with it was because I'm not violent, everything else checked out. And afaik, not all autistic people lash out violently when frustrated. Idk, just wanted to put this out there.