Symptoms
Added Registrar Feature (new custom TLD) is not visible in the list of the registrar's TLDs in
Home> System> Settings> Domains>
Registrar NAME
TLDs
Resolution
Add TLD in a different way:
Home> System> Settings>
Domains
TLDs
For a permanent fix update to PBA-E 5.5.1 or later, since 5.5.1 new feature added for the Registrar automatically appears in the Domain Zones list for the Registrar.