I think (not sure) that they show up under Network Wide/Clients - but they look the same as all other clients.
I have found a quick and easy way that works for me is to search for the subnet assigned to Client VPN.
For example, if you have 192.168.27.0/24 assigned to Client VPN connections...just search for '.27.' in network connections and it will show you all of the connections for the given time period.
If you drill down into the client details, it will show you the last time it connected and when it disconnected (although, my disconnects are hit and miss, think it may be if they truly disconnect vs. a computer timeout or shutdown).
@PhilipDAth is correct. You can find them under Network Wide/Clients. They will show up with one of the following symbols:
Green = currently connected, Gray = Not currently connected.
@WadeAlsup, that's how I drill down to my Client VPN connections as well!