This is the default position of the Properties view. For the different types of selection nodes and edges corresponding tabs are provided.
Empty Area
General information about an opened diagram is shown, and can be edited if no object is selected.
Nodes
Information about nodes is shown, and can be edited if a node is selected. Also, stereotypes can be applied.
Edges
Information about edges is shown, and can be edited if a edge (connector, relation) is selected. You can also specify the kind of aggregation that applies to the properties.