If it is just large tap areas for smallish elements, you could always put a larger box (rectangle, circle, etc.) with no fill and no border over the small element and have that link to the other artboard.
That way the 'invisible' element is the actual tappable one, with the smaller element visible behind it.
Yes, but seems somewhat non-intuitive having to create invisible shapes in "design" mode. It may be nice to have a hotspot tool in "prototype" mode and the added value of a visual reference for all interactive regions. This will also avoid creating clutter in "design" mode and will only be visible in "prototype" mode (e.g. InVision).
IMO "design" mode should be focused on designing, "prototype" mode should be for creating interactions.