When you've got lots of orders and some are at AWAITINGREPLEN and some at NEW, you can't merge orders. Get that the orders have to be at NEW but if you think about it, AWAITINGRELEN will become NEW, it just needs the stock moving. Replens traditionally done by night shift so by time customer is awake, orders have already been processed by early shift......
A similar one has been raised on MST-I-501. Thinking about how it would work, could do with a system setting in Customer Account Settings were we can configure order status where merging is allowed in the same way we can say if an order is at a certain status, don't create a shipping label