No idea (I don’t even have that slider in my Screen prefs, using VESA).
I’m not even sure hey’s syntax allows including e.g. a ‘be:value’ field in the BMessage you send. That would be a nice addition…
It would be nice to add scripting support to the Screen prefs (all prefs really), so you get all the valid commands with a hey Screen getsuites. Then setting would be easy as something like hey Screen set Brightness to 100.
Didn’t @owenca add scripting commands to MediaPlayer last GCI? Maybe as mentor this year, he’d like to supervise such tasks… 