This window is not for a typical curve design session. It is only used in an experimental component for designing swept surfaces using skinning. See Using Skinned Surfaces to Design Swept Surfaces. Since it is experimental and is not stable yet, this window may be changed or even dropped in future version of DesignMentor.
For the details of swept and skinned surfaces, please refere to Cross Section Design, Simple Swept Surfaces and Skinned Surfaces.