There is no API to set IsPrimary for NodeEntryRelation
Jul 27 2017
Aug 29 2017
Closed, Fixed and tested
IsPrimary can only be set via import, or via moving through Catalog UI if it already has a primary node. In case customer uses IRelationsRepository directly to manipulate the relations, there would be no way to set a category is the primary one, and then breaks the ParentLink property.