How to change the first approver of Performance Documents?

Summary:

Seeking on the configuration page to set the first approver of performance documents.

Content (required):

After the worker self evaluation, the performance documents will be routed to the workers' manager for approval. I can find the setting in the approve performance document workflow.

After the manager evaluation, the performance documents will be routed to the manager's manager for approval. I can't find the setting in the approve performance document workflow. How and where in the system configuration to change the first approver of performance documents?

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