There is only one primary NSX Manager in a cross-vCenter NSX environment. Select which NSX Manager will be your primary NSX Manager, and complete the configuration tasks to complete NSX installation, assign the primary role to the NSX Manager, and create universal objects.
The primary NSX Manager is used to deploy a universal controller cluster that provides the control plane for the cross-vCenter NSX environment. The secondary NSX Managers do not have their own controller clusters.