How to add 3rd party application autostart in Gamescope ?

### I'd like to add 3rd party application autostart when Gamescope session loads on system startup.
I've tried things that didn't work but I also don't want to interfere too much with ChimeraOS system to avoid rollbacks or issues when performing updates...

In my case, I just want to start a barrier or synergy (client or server) in order share keyboard and mouse between my ChimeraOS system and another computer on same network.

=> Does anyone knows the "good method" for doing such a thing that won't mess-up the system ?