No, you can’t delete an active used promo code, It will goes under Inactive Status.
You can Active it by clicking on Edit icon of the Promo and enable the status as “Active“.
Step 1: Click on Delete icon of the used Promo Code.
Step 2: Opens a Confirmation popup.
“This Promo Code is already used by 1 Registrants. Do you want to Inactive promotion? ”
Click on ‘Yes’ to Inactive promo Code.
Click on ‘No‘ to exit alert without Inactive promo code.