I'm using a OnePlus 3T and I was never able to edit any of the System Settings.
After some searching around I found out that this seems to be an Android restriction.
But I just recently rooted my devices and found that I could change System Settings with Tasker using:
Command: settings put system buttons_brightness 0
Use Root: YES
So my question is: Could you add a "Use Root" option into AutoTools Secure Settings as a workaround?