We are using the OOTB NetSuite connector and cannot get the supervisor to populate. We have tried setting it to the user name in Netsuite as well as the NetSuite InternalID for the users manager & the display name in netsuite.
InternalId should have worked for you. Couple of suggestions:
Have you tried updating the supervisor field for the employee via REST API using postman? Use internal id in the body to see if you can update supervisor using REST API or not.
Do you have any existing employees with supervisor populated, if yes, then what value do you see in the supervisor field?
interesting we have OOTB NetSuite connector ( uses SOP not REST) and we able to populate superviser with no issues, without any out of box modifications. We get superviser’s display name in that field.