See this thread. The singular VPN per profile is a limitation inherited from AOSP. I dont want to speak for GOS team, but I don't imagine entirely reworking the AOSP network module is a simple endeavor
You may be able to work around this by using an app like RethinkDNS or Orbot. These apps themselves take up the profile's singular VPN slot. You can then configure more nuanced network configs within them - either multiple, simultaneous wireguard tunnels (RDNS), or customize your Tor endpoints (Orbot)