hello. Following up on your observations, what if you work in the opposite direction? That is, after everything is booted and working, never mind the magic that makes it go, you explicitly detach the mouse from the wsmux it picks by default and explicitly reattach it to the mux you want before starting your application? I have the following in my /etc/rc.local to detach the bell from all the auxiliary sound cards it grabs a hold of at boot time. this isn't exactly what you want, but similar commands concerning the mouse, rather than the bell, might get you something that works on boot without requiring plugging and replugging the mouse to get things going?
-thanks -Brian # Turn off the secondary bells on the system (BB 01/28/2021) /usr/sbin/wsmuxctl -f 1 -r wsbell1 /usr/sbin/wsmuxctl -f 1 -r wsbell2
