Watch Fitt's law in your design for the icons. The smaller the icon, the harder it is for the user to click on it. Expand/collapse is realllly small -- too sma

Watch Fitt's law in your design for the icons. The smaller the icon, the harder it is for the user to click on it. Expand/collapse is realllly small -- too small for users to click on, and probably too small to make them want to. The other thing from a visual standpoint you should watch out for is too many horizontal lines of alignment. (tab stops) The eye is hardwired to want to scan for order -- but hierarchical ordered lists like that make it hard for users to absorb the most important thing about your lists-- the content.