Hi @tier, welcome to the forum.
I will argue (as I have argued before) that you basically need a counter going up so you can get the next id in the shared array, which is what xk6-counter does perfectly fine.
And as @ned has explained here and in this issue this can be done if we give access to the global iteration counter of a shared-iterations executor. Also arguably data segmenation is exactly what this about, just that in this case, a simple counter is all that is needed.