How to do VPN split tunneling for specific port(s)?

I was going by this tutorial, looking at the sections for split tunneling with OpenVPN or Windows Powershell (IKEv2).

I'm relatively new to this sort of stuff, so I would really appreciate some help.

To do it, this website says to choose a subnet. I kind of understand what they are, but what I would like to do instead, is just route traffic on one or two ports (e.g. port 80 and/or port 21).

Preferably, I'd like to be able to do it by editing my OpenVPN config file (as the tutorial I linked above says, but instead with ports), but if that can't be done, I'll be happy if it can be done in Powershell with an IKEv2 connection instead.

I've seen some pretty good tutorials for Ubuntu that allow you to do this, but you can't apply them to Windows (because they use iptables, etc).

If possible, I'd like to do it on Windows, rather than switching to Linux.

Can anyone help me understand how to do this? Thanks.

Edit:

Would it be easier to route applications instead? (e.g. Route an app like Zoom around the VPN, but tunnel a game through VPN?) This is just an example, but is that more straightforward to do on Windows?

This Powershell command triggers the VPN connection when a specific app is opened:

Add-VpnConnectionTriggerApplication -Name "<VPNConnection>" –ApplicationID "<AppPath>"

So I assume what I want to do would look somewhat similar to this, except it only applies to that one app. (and it doesn't have to only be triggered when that app opens, it can stay on always).

It looks like I'm going to have to use this Powershell command. It's not exactly what I wanted but it doesn't seem I have any other choice. It's ridiculous that Windows doesn't have something that can do this.