The way to create an empty array in Shopify is assigning an empty string and splitting it.

{% assign our_array = "" | split: "," %}

Now to add stuff to the array we create new array from the object we want to add. We use the double reverse trick for this:

{% assign object_to_add_as_array = object_to_add | reverse | reverse %}

And then we concatenate the two arrays into a new array.

{% assign our_array = our_array | concat: object_to_add_as_array %}

On the internet you find some examples that just uses “push”, but this is an array function that Jekyll added, and is not a part of Liquid.