It already has a bunch of fancy new features:
 - nicer look
 - can search for object name by simply typing it
 - multiple selection (works across layers!)
 - allows to transfer the selection to the diagram
 - tooltips for additional information

Currently missing:
 - reaction to the diagram changes (i.e. auto update)
 - filtering by object type (or anything else)
 - sorting by name or type (or size?)
 - serializing it's position
 - looking into groups
 - in-place editing (e.g. moving objects between layers)
 - enough functionality to also replace the layer dialog
   - move layer up or down
   - add/remove layer
   - hide/show layer
   - rename layer
   - maybe hide toe objects for layer editing (or just view defaults)