Select Assignee from customized application list

If I want to have 2 level approval assignee list based on another application list. How would I could do ?

Code | level 1 approver | level 2 approver
123 Peter Nichael
234 Michael Marget

Hi Edward,

You can use ListLookup control or listLookup function to retrieve approvers from another list. And then use the result in task assignee. BTW, you can use arrayConcat function to connect to results into one array if required.