If you keep two vertices fixed, say the bottom two, then you can adjust the other two to get different WWR. Then, you can write a small formula to adjust the vertices and pass the values in terms of a WWR. Like this:
 FenestrationSurface:Detailed,
  Perimeter_bot_ZN_1_Wall_South_Window,  !- Name
  Window,          !- Surface Type
  Window_Const,       !- Construction Name of the Surface
  Perimeter_bot_ZN_1_Wall_South,  !- Building Surface Name
  ,             !- Outside Boundary Condition Object
  AutoCalculate,      !- View Factor to Ground
  ,             !- Shading Control Name
  ,             !- Frame and Divider Name
  1.0000,          !- Multiplier
  4,            !- Number of Vertices
  0.000,0.0000,2.3293,  !- X,Y,Z ==> Vertex 1 {m}
  0.000,0.0000,[2.3293 - 3.96240*$wwr],  !- X,Y,Z ==> Vertex 2 {m}
  49.91,0.0000,[2.3293 - 3.96240*$wwr],  !- X,Y,Z ==> Vertex 3 {m}
  49.91,0.0000,2.3293;  !- X,Y,Z ==> Vertex 4 {m}
The exact formula will be different for your application.