I mapped Command+Left arrow to a new shortcut in the Keyboard Shortcuts area of System Settings, and now I can't figure out how to set it back to "go back to the start of the line." I have tried:

 1. Changing the thing I'd mapped to Command+Left arrow to something else.
 2. Looking in Keyboard Shortcuts for anything that could possibly be the default behaviour for Command+Left arrow.
 3. Hitting every "Restore Defaults" button I could find in the Keyboard Shortcuts menu.

None of this has worked. Incidentally, this also prevents me from using Command+Left arrow to go back to the previous page in Chrome.

I have the same problem with Command+Right arrow. I am using OS-X Sonoma 14.6.