Other answers suggest going through the Amend process, but in Deluxe Online it only changes the State return, not Federal. Still other answers suggest clicking the "Add a state" button but that prompts to delete the Amended return (which is fine) and then goes back to the same "You filed your 2018 taxes" screen that I started from. But neither Federal nor state are filed, I merely printed them.
Found the answer I was looking for:
How do I change from mail to e-file in TurboTax Online?