To Add Edges
Two workflows are available to add an edge. You can use any one of them as appropriate.
Object-Action Workflow
1. Create or import a shape.
2. Select one of the following sets of mesh elements:
Two or more vertices
Two or more edges
Edges and vertices
3. Click Freestyle > Add Edge. Alternatively, right-click and select Add Edge. A new edge is added.
Action-Object Workflow
1. Create or import a shape.
2. Click Freestyle > Add Edge.
3. Select one of the following sets of mesh elements:
Two or more vertices
Two or more edges
Edges and vertices
A new edge is added.
4. Select another edge or vertex to add additional edge, or middle-click or press ESC to exit from the Add Edge mode.
* 
You can add edges only at the base level.
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