The custom stair is a flexible stair, and you can make very complex stair with it. To use the stair effectively, you need to understand the basic concept behind the stair.
The custom stair is a like a kit of parts. You assemble the stair from parts. The parts can be flights (straight or curved stairs), platforms (landings) and winders. So, you do not design a stair in one go, as you do with the other stair, you design each part, and the parts add up to a stair.