It appears as though this is something that is extremely difficult if even possible based on the responses from both communities. I wish I could help you but I see it as overly complicated myself to even attempt.
Also in the image you can see the Whonix developer provided links directly on the topic
Combined with the needs you expressed in your previous post
Is your computer powerful?
If it’s powerful, open two VMs. One VM without Tor integration using VPN and the other using whonix.
Shared network
Other forums with more technical focus and expertise have answered this question. If they can’t answer it, I doubt anyone here is able to.
I’d suggest re-assessing if this technical solution is required for your threat model, and if there are any other alternatives that are generally better supported. Going into deep technical setups means you are going to have less support - if you are not prepared with this, then you may end up worse than if you chose a simpler solution.