~/.config/environment.d/gamescope-session-plus.conf/usr/share/gamescope-session-plus/sessions.d/steam
deck@LegionGO:~/.config$ cat /usr/share/gamescope-session-plus/sessions.d/steam|grep -i clientcmd
export CLIENTCMD="steam -gamepadui -steamos3 -steampal -steamdeck"