Or any skill that you deeply value for how it helps you, but maybe easily overlooked by an outsider?

I think exercising atleast 2-3 times a week was good for me. Not that I look much different, but I do feel a bit stronger and that is nice. Neck isometrics and bridges too. They really helped with balancing looking at mobile or PC screens.

Learning some keyboard shortcuts was nice. The major one would be Win key + Arrow keys to manage multiple open windows/apps.
Then, finding that I can add commonly used options to the QuickAccess bar in Excel, Word etc. Libreoffice would probably have similar options too.