The idea is for 3d printing.
Many times I design things that won´t fit my printer so there is the need to slit an object but the object I want to print is often composed of many small and not always connected/touching parts.
This is why it would be useful to have a way to slice large constructions and first make them one single object then make them output to stl.
This way we could split a large construction, keep working on it so fixings could be added and then print them on a 3d printer.