concat

concat simply concatenates two arrays.

{% json arr1 %}
    [
        {
            "foo_1": "bar_1"
        }
    ]
{% endjson %}

{% json arr2 %}
    [
        {
            "foo_2": "bar_2"
        }
    ]
{% endjson %}

{% assign arr3 = arr1 | concat: arr2 %}

{{ arr3 | log }}

Above would log array of json objects:

[
    {
        "foo_1": "bar_1"
    },
    {
        "foo_2": "bar_2"
    }
]