You can def get that but targeting the item position within an array.
but, if this is a transaction (assuming from the transaction) or a list, its likely that you will need to process each item within the array, as this would only ever give you the first item (0) within the array even if someone has purchased multiple items. same goes for item_lists.
The problem is that Facebook expects some items inside the array and some items outside the array. And in my webhook I have every item specific field inside the array.
And as @Chris_Bradley mentioned, this is only viable for 1 item inside the array. Not sure how to do it with multiple items.
We have a variable (Tag Manager Template Gallery) that can convert any custom array into datapoints for most popular destionations, but that one is on the web currently, I do have it listed to be ported to the server but I can’t promise any timelines