The file below is a Visual Studio Code snippets file with a lot of useful Unicode characters that I've gathered over years of doing a PhD in theoretical CS.
I've included the source .toml below it. If you would like to add new snippets easily in TOML format, check out my tool https://github.com/bgeron/character-snippets and just pipe the TOML through it.
If you're planning to use this with LaTeX, then check out this .sty file as well.