Gateway group as the destination in firewall rule?

[Pyr0]

TLDR: Why can't I select a gateway group (I'm load balancing two external connections) when defining a destination for a port forwarding rule.

Summary:
Attempting to create the following NAT Port Foward entry:
Int: WAN / WAN2
Proto: TCP/UDP
Destination: Gateway_Group (WAN/WAN1 - Load balanced)
Destination Ports: XBOXLIVE (a firewall ports alias)

Doing all this since my XBOX ONE's are showing strict NAT types (not good for gaming) - I have been following this guide: https://niallbest.com/achieve-full-open-nat-with-port-forwarding-for-xbox-live-via-opnsense/

But get stuck when I attempt to define the NAT: Port Forward steps since I need the destination to go to the gateway group, not a single WAN.

My thoughts:
Why can't I define a alias that lets the firewall know that the gateway group is the destination? But I haven't figured out a way to do this since the gateway_group is not selectable in the drop down.

Thank you for any help you can offer.

[HamiltonWDS]

Trying to load balance for incoming traffic from an external source, well that is different as normally for outgoing traffic from internal sources. I think you may need to explore a plugin for that purpose.
But may work... though not likely, have you tried to use just, "This Firewall" as the Destination?