Mergify: Combine, Merge Orders

Works great for us! Make sure to enable the feature in Mergify → More Settings → Miscellaneous - that can allow it to see orders older than 60 days. Their support chat helped me with this and is very quick at responding! We use this app to merge orders from large pre-order collections. The only snag is international orders, which you may have to merge manually.

A truly reliable order-merging app!
Mergify is exactly the kind of Shopify app you want in your toolkit. It automatically merges orders based on clear, customizable criteria, and the whole system feels solid and well-engineered. Every parameter you might need is there, which makes the setup flexible without being complicated.
The support team is also excellent — fast, friendly, and genuinely helpful whenever you need them. Since installing Mergify, our operations run more smoothly and we’ve saved a lot of time. Highly recommended for any store looking to streamline its fulfillment workflow.

This app works great to merge orders and when I had questions about functionality, the support team worked with me to better understand what was happening. My only desire would be for the documentation to be a little more clear, but other than that, no complaints.