Access via VPN using internal address

How can I tell the app to use the internal address when I’m connected to my home network via VPN?
I believe it uses the home network wifi ssid field to determine which address to use, but can it use for example an ip range?

I solved it with some reverse proxy voodoo.

Hi there I would like to know if this is possible too as my reverse proxy is offline when we have load shedding in South Africa so I only have the necessary stuff running via inverter. The server that houses all my other apps including reverse proxy is down during this time so it would be great if the app could cater to use internal address when connected to vpn.