To add a vertex to a photometric area, solid, or mask, go to
Ribbon: DM Electrical->Point-by-Point Photometrics-> 
Add Photometric Vertex
Pulldown Menu: DM Electrical->Point-by-Point Photometrics->Add Photometric Vertex
You will be prompted to identify the location on the area boundary, solid, or mask where you want a vertex to be added.
Select break point on photometric area, solid, or mask:
A new vertex will be inserted. The appearance of the object will not change, but you will have a new grip that you can use to drag the object into the correct shape.