Currently, once the Nickname field for Temporary Emails is populated, it does not allow the Nickname to be Edited or Removed.

If there are no longer any Temporary Email Addresses in use, the Nickname field should be unlocked for Editing or allow it to be removed and reentered.

This is not to be confused with the Account Nickname, which does allow editing under the Account Profile. This is the NickName field in the Temporary Emails Panel, which can be different then the Account NickName.