COLLECTION - Changing default products order
By default, Shopify displays products in alphabetical order.
However, you can change the default order, or even manually re-ordering your products.
Open the collection you want to modify in the Shopify admin.
In the "Products" box, you will find the default sort order. You can modify it to something else. If you choose "Manually", you will be able to manually re-order the products the exact way you want:
Please note that changing the sort order only applies to the given collection ; you will need to repeat the process for all the collections of your store.