Yes, it can be used this way subject to the router's support of forwarding a port to a broadcast address.
In general, there would the following steps:
Make sure WOL is configured at the target PC and can be woken up locally from the same network.
Add a WOL entry in the Network Scanner application. If your router has a static external IP address, use Add - IPv4 Target. If not, the router needs to be configured to work with a DDNS service like DynDNS, so it can be accessed by a domain name. Once done, use Add - Host Name Target.
The router needs to be configured to forward incoming packets to the port configured in the above step to a broadcast address like 255.255.255.255 or x.x.x.255.
Here is how it's supposed to work:
A "magic" WOL packet containing the target's MAC address is sent to the router's external IP address.
The router forwards and broadcasts that packet within the LAN.
A computer with the MAC address from the WOL packet wakes up.