This would be beneficial for layer names that are long and prefixes are required for a whole suite of layers. At the moment we can only see about 16 characters. If we could extend this toolbar we could see longer layer names that come from for example architectural dwgs.
The Hovering feature is good, however it just doesn't satisfy that 'quick glance at the layer' that I'm sure most people do. I would be thinking, if the bar could be extended with a grip to whatever the user wanted and locked into their toolbar layout then everybody would be happy.
Hovering over the layername in the property toolbar will display the entire layer name.