You can snap to the beginning, middle and ends of a part/group/model's overall bounding box. First enable the 'Pivot' tool from the Main Toolbar:
The click on any of the axis arrows in the Pivot widget and hold down CTRL. This will show matching axis color small sphere to the points where you can snap the pivot:
Currently, you cannot select a specific point on the geometry to snap the pivot, only these predefined beginning, middle, and end points of the overall bounding box.
Thank you Brian