Identifying monitors

[zahlenmeer gmx de]

I am rephrasing my question from a few weeks ago to hopefully be more
precise this time to get an answer:
I save preferences per monitor and I want to load the matching settings
for each monitor at application startup. However, I do not know how to
reliably identify which plugged monitor matches which preferences
section. It is tempting to use gdk_monitor_get_model. But this function
has at least two drawbacks: It is not guaranteed that each monitor has a
model, and it is not guaranteed that the returned string is unique.
Using the index in gdk_display_get_monitor to identify a monitor is also
not a promising idea because one can arbitrarily plug in and out
monitors in different orders.
So what could/should I do?

Kind regards