There really needs to be some form of indication on screen when an order has been split. If not on screen make it available in Template Designer to print something on the invoice. There seems to be no way of knowing an order is split - whatever this reason is, could be out of stock, made in a different department or whatever, but that doesn't mean it won't be posted together.

This doesn't even flag up when in Despatch Console, so the user has no idea that there may be other items for the same customer.