Add More Approvers to One Step (Approval Workflow)
To add more approvers for the same step, add more records to the ApprovalWorkflowSetup table, with the same WorkflowType and Step ID, but with different values in Approver ID field.
Example of more approvers for the same approval step
Limitations
For a single step you can only combine approvers with the same Approver Type. For example, do not combine the approver record with Approver Type USER and USER GROUP.