The protected domain can be renamed through MSA GUI.
Please follow the below procedure.
Login to vCenter and navigate to MSA GUI
vCenter > DataCenter > Configure > JetStream DR and click on the edit button.
Enter the Protected Domain name in the field and click on configure button.
The Protected domain will change successfully.
Note: Incase of a CFO in place renaming of PD might take some time for the changes to be effective.