I don’t code, but I do know you can add new collision channels to your projects under Edit → Project Settings → Collision. Perhaps you can just refer to the new channel in the same manner you refer to the Pawn/WorldStatic/WorldDynamic channels already?
In Blueprint I simply create my new BP, then set their collision to either ignore or overlap each other.
This is the properties for a Basic Enemy BP. Notice at the bottom there is 3 new channels, Enemy, Player and Bullet. I have set the Enemy Collision to Ignore. Hope that helps.