You can modify completed cards, but not in-progress cards
As @Wizcat mentions both of these would be fantastic to have added as feature suggestions on the feedback forums: https://matchplay.uservoice.com/ (as two separate entries, please!)
I added the card format based on input from the German Pinball Open tournament director -- no one else spoke up to offer feedback at the time -- so the implementation tracked pretty closely with their needs. I can totally see these changes being improvements for all TDs! It's just a question on finding time.
@Wizcat I can guarantee that I won't have time to make any changes before your tournament