information in this article applies to:
How do I create a set of winder stairs?
Begin by drawing the stairs away from any walls to get unrestricted editing.
Winders must be in a room with proper room definition.
You cannot create winders in an area composed of only 2 corner walls. If this configuration is needed, enclose the area in with invisible walls so that a room area is defined.
Alternatively, Right click and drag will enable this alternate drawing mode as well.