WIDGET_API void XPPlaceWidgetWithin( XPWidgetID inSubWidget, XPWidgetID inContainer);
This function changes which container a widget resides in. You may NOT use this function on a root widget! inSubWidget is the widget that will be moved. Pass a widget ID in inContainer to make inSubWidget be a child of inContainer. It will become the last/closest widget in the container. Pass 0 to remove the widget from any container. Any call to this other than passing the widget ID of the old parent of the affected widget will cause the widget to be removed from its old parent. Placing a widget within its own parent simply makes it the last widget.
NOTE: this routine does not reposition the sub widget in global coordinates. If the container has layout management code, it will reposition the subwidget for you, otherwise you must do it with SetWidgetGeometry.