You can create a winding stair by drawing a pair of arc polylines, marking the outside edges of your stair. Draw a centerline polyline as a guide. Then create a multi landing stair along that centerlined path, making sure your stair is wider than the widest point of your stair at any point. Then, right click the stair, customize edge, project and follow the prompts. Walah! Winding stair, any path you desire.