network – How to Forward Specific Traffic Through VPN?

Before we begin, I must admit myself as more of a novice in the world of networking. Thank you.

I would like to send specific traffic through my VPN, through a local machine, or through WSL.

ie. Traffic via/related to would go through a VPN (local machine, etc),
BUT, would still be unVPNed in whatever normal means.

I haven’t found any sources that have described or shown or asked how to assign a specific IP or address to be redirected to a VPN. Maybe they are everywhere and I am just missing them, or I don’t know how to ask for it correctly, or maybe it is something so basic I am missing it.

I thought I may have been able to find what ports certain website addresses attempt to access specifically, but if I understand correctly, ports are more like highways and allow multiple lanes of traffic to flow, so I would be rerouting an entire network as opposed to a single site/address. Maybe I am over thinking this, or going about this wrong.

I also went to check the settings within Mozilla and ProtonVPN, but didn’t see anything to what I had in mind, though again, I could have discovered it and not known I was looking at it. ProtonVPN would allow me to choose custom ports, but not specific sites/addresses, and Mozilla offers to set a Manual Proxy, which appears close to what I am looking for, but seems more focused on proxying all but a select few sites; I want that in reverse.

**OS:** Windows 10  
**WSL:** Pengwin  
**VPN:** ProtonVPN  
**Browser:** Firefox Developers Edition

(I don't know if any of that is important here, but there it is)