How can we populate the locked "All WAN interfaces" group we see in CAPC under Inventory > All Items?
Any version of NFA
In the NFA UI there is a page in the left bar under the Interface section called "Physical & Virtual". Find the device in question that owns the interface(s), edit the interface and change the type to "WAN". This is essentially overriding the interface type. After doing this sync the NFA data source and the interface will populate the locked "All WAN interfaces" group in CAPC