To "Delete" a PIN code you will go to "Visitor Access" and click on the 3 dots to the right of the PIN Code you are trying to "Delete". Then click "REVOKE" this will deactivate the PIN code. It will warn you that the PIN code will be deactivated and then click
To create a new one click on the purple "+" sign at the bottom right corner and you will be able to create a new pass. For step by step please go to the "How to do I create a PIN code for a Visitor?"