X11: How to set the primary monitor using a script

I need to use xrandr to add and use my monitor’s native resolution. It mostly works but sometimes KDE will switch around the monitors. I need to open the settings and switch it back. Especially after updates this happens. (DDI is b0rken)

I need a command to tell KDE: Use this monitor as your primary screen.

I’m using OpenSuse Tumbleweed x64

$ cat .config/autostart-scripts/xrandr.sh
modeline_1680="1680x1050_60.00  146.25  1680 1784 1960 2240  1050 1053 1059 1089 -hsync +vsync"
# modeline_1680="`cvt 1680 1050 60|sed -e '1d;s/^Modeline //;s/"//g'`"
xrandr --newmode $modeline_1680
xrandr --addmode DVI-I-0 1680x1050_60.00
xrandr --output DVI-I-0 --primary --mode 1680x1050_60.00 --pos 1920x0 --output DVI-D-1 --mode 1920x1200