When we select a shape in Impress, the Property panel (at right) shows its various properties. 

These are divided into five sections: 
Character, paragraph, area, line, position and size.

But none of these contain the shadow property.

As a result, the user still has to look for these controls through a separate toolbar. This defeats the very purpose of putting all properties in a single place, for easy access.

Desired:
Please add "shadow" property to the pane. It should be added as a separate property, because the shadow is applied to both "Line" and "Area" of the shape.