The app you mentioned exclusively focuses on automated order merging. If a merchant requires the ability to preview mergeable orders before merging them, it may not be a suitable app. However, in such cases, Mergify can serve as a suitable alternative.
Mergify merges orders through smart suggestions in addition to automatically merging orders. Smart suggestions mode provides merchants with the flexibility to choose specific settings for both the original orders and the final merged order. This allows them to verify whether the orders should be merged or not. Mergify empowers merchants to customize different properties for individual orders.
Mergify | https://apps.shopify.com/bestapper-mergify
Merge & combine orders to save on shipping costs