Is it possible to create a collection and add it to an existing array?

Hi everyone,

I just begin to use Make two days ago to synchronize Shopify orders with Axonaut and really like the way to do things here.
My scenario is working to get the order from Shopify an create an invoice in Axonaut.

But I am still missing something in my invoice which is the cost of shipping which I would like to add as a product. Shopify store the information outside the product list, so I would like to add one more “product” in the product array that I pass to Axonaut based on these informations. But I don’t how to create a collection that I could add to an array and would look like something like this:
“name”: “Livraison standard avec suivi (4 – 6 jours)”,
“price”: 7.4166667,
“chapter”: null,
“quantity”: 2,
“tax_rate”: 20,
I am planning to add this collection/object to an array (coming out of an aggregator) with the add function.

I don’t know if what I would like to do is clear… In short, I would like to create (from information collected here and there) a collection of item called “A” that I could add to an array containing a list of “A”.
It maybe simple but I couldn’t find the way to do it.

Thanks in advance for your help,