The Management Model tool under the Tools menu (bottom right corner) is very useful, but the model tree shown at the left doesn't visually distinguish between "value nodes" and the "non-value" nodes. Like this, it's pretty easy to click on a node only to read "Please select a value node". I believe that these "non-value" nodes should be somehow visually distinguished.

Some ideas:

• value nodes should use a "hand-like" cursor when hovering (cursor: pointer in CSS), while non-value nodes should continue to have a normal cursor
• when clicking a non-value node name, it should collapse/expand (currently, it only collapses/expands when clicking on the +/- button); downside is that it this would be inconsistent with value nodes
• using colors and bold/italic to highligt value nodes and "lowlight" non-value nodes