With a list trigger, Is there a way to tell the automation to loop through all the filled rows in the Google Sheet rather than hard coding to the last row?

the List trigger stops when it runs out of filled rows so if you set it to 2 and turn it on, it should be doing what you want.

If you want to get really custom (no code but technical thinking) you could build some logic in apps to use the “find rows” action and looping / filtering there to decide yes. Comes Feb to creativity