Whenever I accidently click something by accident, you can try finding the Undo command at Edit > Undo to see if all the Ch 1’s can turn back to what its supposed to be.
Or you can also change everything back to its default settings following these steps:
To reset Adobe Premiere Pro preferences to the default settings:
- Hold down: Alt/Options on Mac or Alt on (Windows).
- Keep holding down the Alt key, and click on the Premiere Pro app icon to open it.
- In a few seconds, it asks you “Are you sure you want to reset your preferences?”. Click OK.
Hope it helps and best of luck!