Firefox settings setting - about:config/layout.css.devPixelsPerPx - reset and set value by external script?

Question

Browsers

there is a certain set of FF profiles, which, for various reasons, already regularly migrates to Lunicus and Windows. in Windows, this parameter picks up the default setting visible, but not in Linux. sometimes you also want to set a non-default value in one fell swoop to all profiles, but maybe then in the same crowd and reset,
does anyone know of the present short path to the goal? for C#, targeting files will suffice, or, perhaps, information about pitfalls,
but I can accept as a gift, a working fragment on Js, for example, sharpened by node.js

Answer 1

kb.mozillazine.org/User.js_file - description of working with the Firefox configuration file.