It really makes not sense to me why would you require a second list (of indices) in order to sort one list of values.
You don’t, the [A] input is optional. If you only want to sort numbers, just use the [K] input alone.
I didn’t check that, I assumed I have to provide every time. So I struggled whether to use range or series
Uhm, David,
It’s kind of the other way around than what I would need.
I need to sort the values not the indices. 
Yeah, plug your values into K, and they’ll be sorted. A is optional. If you need some other things to be sorted synchronously along with your values, then you use the A (B, C, …) inputs.
Will I then get the reordered indices?
No. I thought you didn’t care about any indices and just wanted your values sorted. If you need the index then I’m afraid you’ll have to provide a list of unsorted ones.
Check this thread about the usecase:
I’ve logged it under RH-50870