From X-Plane SDK
WIDGET_API void XPUCreateWidgets( const XPWidgetCreate_t * inWidgetDefs, int inCount, XPWidgetID inParamParent, XPWidgetID * ioWidgets);
This function creates a series of widgets from a table...see XPCreateWidget_t above. Pass in an array of widget creation structures and an array of widget IDs that will receive each widget.
Widget parents are specified by index into the created widget table, allowing you to create nested widget structures. You can create multiple widget trees in one table. Generally you should create widget trees from the top down.
You can also pass in a widget ID that will be used when the widget's parent is listed as PARAM_PARENT; this allows you to embed widgets created with XPUCreateWidgets in a widget created previously.