Everything that happens after the order is placed, in one place: order changes, returns and warranty, delivery problems, follow-up offers and reminders.
Self-service order changes. Buyers fix the address or swap a size from their account page, while the order is still open. Each change is written back to the order.
Returns, warranty and delivery problems. One form per case, with photos where they help, and a single screen in the admin where the shop answers.
A second sale, without extra work. A post-purchase offer, a coupon for the next order, store credit, and replenishment reminders sent through the shop's own email.