Tracking down MACs from a switch can be very beneficial. You can use the information from the MAC table to track down where a device is plugged into, or if there is some kind of loop in the network.
This command is used from the Fortigate to drill down to the Fortiswitch. I do believe it would also work directly from the Fortiswitch.
To display the whole routing table:
diagnose switch-controller switch-info mac-table
Lets say I need to look for the last 4 of the MAC to find exactly where this device plugs into.
diagnose switch-controller switch-info mac-table | grep 3a:fe
00:60:6e:ec:3a:fe port1 1
Now we can see that device is plugged into port 1 of the switch.