Argument: 2-element nested vector
Result: None
Valid for: Tree
The Shownode method scrolls the tree so that a particular node is displayed at the top, or (under Windows) makes a particular node the currently-selected one or the drag-and-drop target.
The argument is a two-element nested vector. The first element is a character vector, one of 'select' 'drop' or 'firstvisible'.
The second element is the node identifier (or 0 or 'none' to remove the attribute from the currently selected node or drag-drop target).