Specify a final approver
You can designate a final approver for scenarios where the approver is the person who submitted the document for approval and the "disallow approval by submitter" is being used. Follow these steps to specify a final approver.
In the workflow editor, right-click the approval element, and then select Properties to open the Properties form.
In the left pane, click Advanced settings.
Select the Use final approver check box.
In the list, select a user to be the final approver.
Reference:
https://learn.microsoft.com/en-us/dynamics365/fin-ops-core/fin-ops/organization-administration/configure-appro
https://learn.microsoft.com/en-us/dynamics365/fin-ops-core/fin-ops/organization-administration/configure-appro