How does this differ from "Submenu Column Default"? If you set "Submenu Automatic Columns" to 5, it'll create 5 even submenu columns and automatically divide the child items of this item into those columns, organized top to bottom.  If you set "Submenu Column Default" to 1/5, each child item will be 20% (1/5) of the submenu width and be organized left to right.  In practice, you'd use "Submenu Automtic Columns" for submenus without column headers, and the "Submenu Column Default" setting for submenus with column headers