U4919DW, built-in KVM switch with second display

I want to use two MAC with one keyboard and one mouse with the built-in KVM switch on the U4919DW. And I want to connect a second display as dual monitor. Is it possible to cascade and switch with the second display using the builtin KVM switch on the U4919DW?

First Mac       

     |   

     |  --->  builtin KVM U4919DW --> U4919DW  ->  Second display

     |

Second Mac 

Or do I have to use a usual separate KVM switch like TESmart Dual Monitor KVM instead of built-in KVM switch in U4919DW?

If I need to buy KVM switch for it, do you know which KVM switch works with U4919DW with 5120x1440 resolution?