As we are using pasystray as a daemon to notify volume changes, we decided to patch the desktop launcher and add a script which will run pasystray with this options enabled.
Please note that the script was necessary because --notify=all flag in PipeWire gives a lot of notifications (even when pausing a video), and we only needed source and sink changes.
To do this we use the flag --notify={sink,source}, which seems to not work on a desktop launcher, but in a script. When using PulseAudio, the --notify=all flag would be enough.