My problem:
I use a laptop with two monitors:
* 2560x1440@60Hz at home
* 1920x1200@60Hz at work
(so, only one monitor at the time)
Unfortunately, laptop's video adapter do not support 2560x1440@60Hz monitors so the maximum resolution I can set up for the home monitor is 2048x1152@60Hz. However, I can generate a custom modeline with reduced refresh rate but with full resolution. To make it permanent I can write Xorg's config file like this:

Section "Monitor"
    Identifier             "HDMI1"
    ModeLine               "2560x1440_50.00_rb" 200.25 2560 2608 2640 2720 1440 1443 1448 1474 +HSync -Vsync
    Option "PreferredMode" "2560x1440_50.00_rb"
EndSection

The problem is that Xorg have no way to apply this options only for certain monitor (neither by serial nor by something else) (that means that I will have good configuration at home but completely broken at work). The only way available to filter monitors is by port (option 'Identifier             "HDMI1"') but it do not suits my needs.
Even worse, after applying such kind of a config, kscreen sometimes stops distinguish monitors.

So, it will be very useful to have some way to do fix that. One of the options could be launching a user script after connecting a monitor before kscreen apply his configuration.

Reproducible: Always