Once a domain name is registered, it cannot be deleted.
However, it is possible to hide (deactivate) a domain by following the steps below.
Hiding a domain
Click on Scan Menu > Domain > Action > Eye Mark (Disable)
Re-display a domain
Click on Scan Menu > Domain > Show Hidden Domains.
*You can also enable a domain by clicking on the eye mark (Enable) as in the case of hiding a domain.