How to configure 2 FortiGate's to talk to one another

I have 2 FortiGate 51E's that are at remote sites but connected together using a LAN port on each firewall, connected over an ISP provided LAN Extension. Both of these FortiGate's are on the same private subnet and talk directly to each other.

Is there a functionality available where I can let each device discover each other? Connectivity and traffic routing is working fine, I was just wondering if there was a similar functionality like the Managed FortiSwitch interface where I can see each hardware device connected to each other and was wondering if that was a thing, and if so, what other additional functionality would that provide?

Both FortiGate's are running FortiOS v6.0.12 build0419 (GA)