I've found documentation on commands for running tests, running scripts, and running other manual processes useful even if I've run the commands before many times, and even if I was the one who created the commands. Documenting anything you find yourself looking up a lot online, or in your Terminal history would probably be useful even at the beginning just to reference for myself.

As time goes on and the company grows, I think reasoning becomes useful to document. Why were technical decisions made in code changes, why were tasks deprioritized, why did tasks grow in scope or reduce in scope over time?