proper place for xrandr script to run before sddm?

Hi *, on my notebook I use a small script to handle the connected graphics ports via xrandr. This script has to be run before sddm-greeter gets started. For a long time now the script was started from [/usr]/etc/X11/xdm/Xsetup, because I couldn't find a better place for it. It is annoying, though, that Xsetup gets overwritten with every update of xdm. What's more annoying, is the fact, that no .rpmsave file is created during update, despite the fact I had modified the file. Is there a better/proper place for a script like that, where it can survive an update unchanged? Something like Xsetup.d/? TIA. Bye. Michael.