You can use Object Configuration Management Module to disable the action related to PO approval. Check for the deployed actions from session Deployments by Package Combination(ttocm0111m000). Refer Infor LN Integration Guide for Infor ION Workflows and Monitors for more information.
Note - Deactivating the OCM deployment might erase the approval history data. Hence following the recommended steps, you can create a new OCM deployment for PO Approval without the approval action added and then activate this new deployment. System will automatically deactivate the current deployment. Check KB#1696639 for more info.
Unless you try to do something beyond what you have already mastered, you will never grow!