Instant Stair isn't a rigid, one-size-fits-all tool. It offers extensive options for customizing the look and feel of your stairs. You can choose from several construction types, including closed (with stringers), open (without stringers), treads-only, or a combination of these options. You also have control over nosing profiles, materials, and texture alignment.
Vali Architects currently distributes "Instant Stair" as a paid commercial plugin . It is part of their "Instant Architecture" suite. You typically purchase a license from their website or via the SketchUp Extension Warehouse. instant stair plugin sketchup free download