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.
Step 1: Click on Delete icon of the used Promo Code.
Step 2: Opens a Confirmation popup.
“ This PromoCode 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.