1. Go to /usr/share/xfce4/ 2. Side Pane > Tree 3. Disk I/O gets faster because (as it seems to me) Thunar is scanning each displayed directory of /usr/share/ to see if it has or has not a directory(-ies) in it. Needless to say in this realm that this practice is bad for machines with lesser resources, if I am not wrong.
It is but its the only way to show a proper tree.