The display buttons appear to the left of the main window of the upper Scene panel. They control display of the hierarchy in the window.
These buttons correspond to choices on the Display menu.
When on, the hierarchy displays thumbnails. Default=on.
When on, the hierarchy includes materials. Default=on.
When on, the hierarchy includes maps. Default=on.
When on, the hierarchy includes objects. Default=on.
When on, the hierarchy includes sub-materials and maps applied to material channels. Default=off.
When on, the hierarchy includes unused map channels. Default=off.
These two options toggle each other.