Basic configuration for user firewall setting?

What is the basic usage to setup port forwarding via user firewall setting? I don’t see it in whonix’ documentation. Please point me in the right direction, thank you.

It’s very uncommon. Therefore not documented.

Port forwardings in the classical sense are not anonymous.

Unless you want to do some local thing (such as ssh from the host into
Whonix-Gateway/Workstation, which is documented), there is no use for it.

For incoming connections, there are:

Outgoing PF configuration?

Well… I am testing it out via Kali to Whonix Gateway workstation so I will need to set a LPORT for listener.