The caseTemplate request returns the format for the optional fields (Custom and Secondary). This can be used as a reference or for copying into the body of a new request. The return reflects the current customized fields for a group.
The (current default) return has the groupIdentifier and groupScreeningType (CASE_MANAGEMENT_AUDIT, ZERO_FOOTPRINT), followed by the customized fields (defaults:Reference, Territory, Primary Contact)
Next the secondary field watchlist with secondaryFieldsByEntity (individual, vessel, organization) and secondary field passortCheck with secondaryFieldsByEntity (individual).
Let me know if you have any more API questions.