That's a good one! I started a "Linux diary" in which I wrote down what I hoped to accomplish, what I did to make it happen, whether or not it worked, how I fixed it - even if I just gave up and reinstalled.
I use Geany as my text editor because by default it remembers all opened tabs upon exiting. So when I next open Geany, I have that text file (actually I have a few) where I keep all my useful notes and terminal commands opened automatically.
1. the full syntax for the dd command, together with the target USB device name (/dev/sdd) on my machine, and also the lsblk command, just so I never forget and type /dev/sdc by accident, which would wipe my DATA PARTITION.
[even though MX's live usb tool now has an easy way to use the dd command, I multiboot so this command is helpful while I'm booted into another distro]
2. my older Brother scanner driver has an issue where the files are installed in an folder location that is no longer accessed by scanner programs. So I have all the terminal commands ready to create the necessary symlinks to the appropriate folder location whenever I install the scanner driver in a distro.