It's quite visible when the focus is on the left-pane,

but when moved to the right-pane

the LEFT-PANE highlight becomes a light gray that's nearly invisible to me against the gray background.
Win8.1, BRU3.0.0.1
Admin wrote:Hi, no problem we will look into the issue with the highlight color being too light and give an option to change it.
BTW if you do not use the tree it can be hidden with F11.