Places a new item in the tree view control. The text assigned to ITEM-TO-ADD is placed as a new item in the control. Its position in the hierarchy is determined by the PARENT and PLACEMENT special properties. The return value from this property is the ID of the new item. If the new item is successfully added, the ITEM property is set to point to this item (this makes attaching a bitmap or hidden data to the item easier — see BITMAP-NUMBER and HIDDEN-DATA).