Insert/Delete a Vertex in "By Shape" Curtain Wall

The Insert/Remove Vertex tool can be used to change the outline of Curtain Walls that were placed using the By Shape option.

Select Insert Vertex from the ribbon.
Click on the curtain wall near where you want the vertex to be inserted.
The nearest edge of the curtain wall "shape" becomes selected. The new vertex is attached to the pointer.
Click at the location where you want the vertex inserted.
The vertex is added, and the curtain wall is updated.

Now delete a vertex you do not want:

Select Delete Vertex from the ribbon.
Click on the curtain wall near the vertex to be deleted.
The vertex is deleted, and the curtain wall is updated.