OrderEditing.com

This app has been a game changer for us. Letting customers edit their own order after checkout has cut down on so many "can you change my order" emails, they just sort it themselves, quickly and easily. It works exactly how you'd want it to, and the support team is fantastic on top of that: responsive, helpful, and genuinely across their product. If you're on the fence, do yourself a favour and give it a go. Highly recommend!