Did not know about 'user.js', thanks! I guess creating a document that lists all my overrides was the first step. Now I have to figure out how to create a user.js that works on Linux, Macos, Windows, and maybe Android?

Same file works everywhere. Just leave out the ones that are different on platforms:

- browser.download.dir

- browser.helperApps.neverAsk.saveToDisk

And instead of making a "google doc" a plaintext file would be better.