You can choose to use Screen Plane only, Layer Plane (Working Plane) only, or both.…
Vectorworks Tip #108 – 3D Modelling – Working Plane Palette
Vectorworks has a working planes palette that you can access from the Window > Palettes menu. This palette can be used to save, delete and activate working planes. But you don’t have to use this palette. You can access and recall all the working planes from the Active Plane menu.