Hi Im using a RPi4 as a second desktop.
Arandr doesn't show the max resolution my display is capable of (1280x1024)
Ive created a new modeline using xrandr/cvt and added that so that arandr successfully sets the new resolution.
However when I reboot the pi the new modeline is no longer present.

How can I 'save' the new modeline so that the pi will boot with the new resolution?

Ive added the following to re.local ..
xrandr --newmode "1280x1024_60.00" 109.00 1280 1368 1496 1712 1024 1027 1034 1063 -hsync +vsync
xrandr --addmode HDMI-1 1280x1024_60.00
xrandr --output HDMI-1 --mode 1280x1024_60.00
this fails on boot but works if rc.local is run from a terminal. I would like this to happen at boot .

Any ideas?

Sorted! I think
In /etc/X11/Xsession.d I've created a file 99set_res_1280_1024. The name I don't think is critical bar the "99".
The contents are ..
xrandr --newmode "1280x1024_60.00" 109.00 1280 1368 1496 1712 1024 1027 1034 1063 -hsync +vsync
xrandr --addmode HDMI-1 1280x1024_60.00
xrandr --output HDMI-1 --mode 1280x1024_60.00
and that's it..
Ive booted the pi several times and each time it has the required resolution. :-)))