You can configure what you see in the Navigator from the Setup - Settings dialog. The Navigator has three nodes, Blocks, Symbol and Nets. Each can be used to control what is displayed. You can switch off different objects, define what is displayed in the labels and tooltips etc. For large designs you could try the following:
Blocks : Hierarchical, Label =$(name), Info Tip $(Name)
Symbols: Display Hierarchical Only. If you want to see more information try modifying the Label Format to something like $(REFDES) ($(Symbol))
Nets : Switch off the display.
Play around with the label options, though we provide a few pre-defined options you may display any available Property (Attribute).
Robert, that was exactly what I was looking for! Thank you very much.