First copy default.pa to ~/.pulse if you do not have it there already
mkdir ~/.pulse
cp /etc/pulse/default.pa ~/.pulse/
Open ~/.pulse/default.pa in a text editor and add this for each audio channel you want
# Make a dummy sink for split audio
load-module module-null-sink sink_name=sinkname
update-sink-proplist sinkname device.description="description Audio"
update-source-proplist sinkname.monitor device.description='Monitor of description Audio'
load-module module-loopback source=sinkname.monitor sink=devicename latency_msec=1
Replace sinkname with a unique name for your audio channel, and update "description"
to give a descriptive name to the sink.
Replace devicename with your audio speaker/headphones device name, you can find those with the command below
pacmd list-sinks | grep -e 'index:' -e 'name:'
the * indicates which device you currently are listening to.
Once you are done, restart pulseaudio with
pulseaudio --kill
If pulse does not auto start again just run pulseaudio --start
Then you can find your new audio channels in pavucontrol
and you just change programs that play audio to play it to your new audio channel.