How to router from external IP to internal IP using opnsense

Question

What rules do I need to create in OpnSense firewall to allow routing of packages from external interface to internal, without masquerade? Let me explain: I have an gateway running OpnSens with a valid IP A.A.A.A (WAN interface) and internal IP 192.168.100.X (Lan interface). All devices under LAN can navigate using NAT/MASQUERADE without any problem. I also have another computers running with valid IP in the same network from gateway (external network), A.A.A.A. I need these machines to have access to internal IP 192.168.100.X, without using ports.....just routing packets. I'm aware that I will need to add an static route entry in every machines with the A.A.A.A as router for network 192.168.100.X......but do I need anything specific in OpnSense to allow this external traffic to internal IP's? Again: not a port forward, but just routing packets with destination for 192.168.100.X.