It might be an array, but the only funtions I could get to work with my test array are item() and slice().

There is turning the array to text with concat() appending it and then making it back into an array with split() but it’s cumbersome.

let myArray1 := [1, 2, 3];
let myArray2 := [4, 5, 6];
let myArray3 := myArray1 + myArray2;
let myArray4 := [item(myArray3, 0), item(myArray3, 1), item(myArray3, 2), item(myArray3, 3), item(myArray3, 4), item(myArray3, 5)];
alert(text(last(myArray4)))

All the Ninox functions worked doing this and myArray4 could probably be initialized using a loop. Still, kind of cumbersome. I tried using concat() on myArray3 and all I got back was a single string of 123456.

maybe this helps?: https://docs.ninox.com/en/script/functions/array

This should answer your question: 

https://forum.ninox.com/t/p8y31x3/how-to-iteratively-add-items-to-a-new-array

Let f := x + y

f

The only known way, as far as I know, to add something to an array, and get an *array* as the result, is to use the "array()" function. The function takes two arrays as arguments, and returns their concatenation as a new array. To add a single element, of the same type as those already in the array, one must first convert this element into a single element array:

newArray := array(oldArray, [addedElement])

Alain Fontaine said:
The only known way, as far as I know, to add something to an array, and get an *array* as the result, is to use the "array()" function.

 Günther posted a solution nearly 5 years ago in this thread - Universal array handling when array items are not text strings. I posted an example database in this thread - Numeric array variable initialization that expands on his solution to add inserting, deleting and replacing elements in an array.