Scroll bar thickness is unaffected when set below 4. There appears to be a minimum size in place that prevents the scroll bar from being set to a size lower than 4
Result: The scroll bar thickness appears unaffected by values less than 4
Expected: The scroll bar thickness would lessen as the number is set below 4
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-72558 in the post.