Unfortunately, there is no documentation regarding delegation of approval requests. To delegate approvals to a user manager a PowerShell script executed in a Custom Command or Scheduled Task can be used. For example of the script, have a look at the following page from our repository: https://www.adaxes.com/script-repository/delegate-approvals-to-assistants-and-secretaries-s389.htm.
For example, to delegate all pending approval requests to a manager of a user manager if a custom Boolean attribute is set to True, you can create a Scheduled Task executing the mentioned above script. The script will be executed if the target user is a manager (the Direct Reports property is not empty), the user has a manager (the Manager property is not empty) and the CustomAttributeBoolean1 property is set to True. Finally, the Scheduled Task configuration will look like the following:
Should you have any questions or need clarifications, please, provide us with all the possible details regarding the desired behavior and we will get back to you with instructions.