Out of the box this is not possible. However, you can achieve this by making use of the absolute positioning of an element on top of the header of the groupbox. See https://www.w3schools.com/css/css_positioning.asp for more information on position. Please note that an absolute positioned element is positioned relative to an element with the ‘position: relative;’ CSS applied to it.
Hope this helps.
You can use the Accordion widget from the Marketplace for this requirement.