In which file is stored the screen backlight brightness settings?

I would like to make a Debian 12 Live system for a laptop, from another computer that has an external display without backlight settings in the operating system. I need to know the file where is stored the backlight brightness settings, to copy it in the Live system, so that the backlight will be already adjusted when I will boot the live system. The live system will use MATE desktop environment, a fork of GNOME. I wonder if the backlight configuration is part of gsettings ? And so, which file I will have to copy, once the backlight brightness adjusted ?