How can I add Shapes to an existing group? (without destroying the group shape)

The only thing I found in the docs for a Group-Shape is the following:

>Shapes.All method
>Gets the shape range
>Function All() As ShapeRange
>The All method returns a or sets a shape range that contains all the shapes from a Shapes collection.

Although it states, that you could set a shape range, this doesn't work. The function doesn't take an optional argument and I guess it's just a mistake.

I think there should be some way because we can do this easily in the GUI.

Do I miss something?