I think in Pro the Stairs Defaults are chosen by the Template you use to start the Plan ( Cottage,Arts and Craft,Urban Chic etc) and not all of them are changeable IIRC.... eg the type of Rail or Newel   these are some Pics I made years ago of each one for my own reference , not sure if they still are all the same....     amer.cas. A&C Col. Cottage Default Med. T.Trad. U.Chic