FMutableParamExpandableArea ( [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [SExpandableArea](API\Runtime\Slate\Widgets\Layout\SExpandableArea) > & InExpandableArea, [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [SVerticalBox](API\Runtime\SlateCore\Widgets\SVerticalBox) > & InVerticalBox )