Setup Flow automation to send a scheduled email to certain customer segment

Thank you for the question. I missed that point in the solution. To remove the tag, you can add the Start custom customer workflow action right after we add the processed tag with the Specifier set to empty processed tag (postponed):

You also need to create a separate workflow that starts with the trigger Custom customer trigger triggered, where you add the tag removing action after 71 hours (so that the mailing can happen again after 72 hours):