an application to onboard new bank customers create child cases for each account that thecustomer...

To configure a report definition that lists new customer cases created in a given day and the average opening balance for all account child cases for each customer, you should use the "class join" feature in Pega. This feature allows you to join data from different classes, which is essential when dealing with cases and their child cases. Specifically, you can create a join between the customer case class and the account child case class to aggregate the average opening balance.