External Contacts in HR Help Desk

Summary:

We are implementing HR Help Desk and Case Management for a client who is also migrating a significant number of SRs and Cases. As part of that migration in their legacy system they have external contacts listed in their SRs and Cases. Instead of housing this data in custom fields in HR Help Desk we would like it to behave like it does for Case Management, where we are able to Add Contacts and use the Add Contacts SmartAction however in HR HelpDesk the same list of external contacts do not appear, how do I enable agents to be able