To Add a Blend Vertex
The method you use to add a blend vertex depends on whether you use selected sections or sketched sections to create the parallel blend.
Selected Sections
If the section creation method is 
Selected sections:
Selected sections:1. With the Blend tab open, click the Sections tab.
2. Under Sections, select the section to which to add a blend vertex.
3. Click Add Blend Vertex.
Sketched Sections
If the section creation method is 
Sketched sections:
Sketched sections:1. With the Sketch tab open showing the section sketch to which to add a blend vertex, select the vertex of an existing geometry entity.
2. Perform one of the following actions:
◦ Click > > > .
◦ Right-click the vertex and choose Blend Vertex.
A circle appears at the vertex. More than one blend vertex can be created at the same point. Each additional vertex will create a concentric circle of increasing diameter.