Hi,
This is already possible. You can use AmneziaVPN (it supports Split Tunneling) client instead of AmneziaWG. You can now import our configuration files one-by-one. We will make announcement slightly later after the testing is fully done.
See my screenshot down below. Simply download AmneziaWG configuration file via WireGuard generator for specific country and import it to the client.
I tried using your option, but I found it less convenient than this app.
What I didn't like about Amnezia is that there are constant interface bugs. For example, it shows that the VPN is off, although it works. Split tunneling by applications also works strangely. Instead of allowing me to add several applications, I have to exclude "hundreds".
Personally, I have amnezia with split tunneling, either it doesn't want to start at all, or it takes several minutes to load. The application that I managed to find starts instantly and I haven't found any failures yet.
P.s. Later I checked it on Android and in Amnezia I was able to select the right application for split tunneling right away. But the connection itself took about 3 minutes.
Attached a screenshot with split tunneling settings.