Unable to delete or add Approval Process Step

Salesforce does not allow adding, editing, reordering, or deleting steps in an Approval Process once it has been activated. This restriction exists to protect data integrity — any records currently in-flight through the approval workflow rely on the existing step structure to route correctly. Modifying steps mid-process could cause approvals to skip steps, route to the wrong approver, or fail entirely. To make structural changes, the Approval Process must first be deactivated. This is the expected behavior, the workaround is to clone the existing Approval Process.

To remove or add an Approval step:

1. Navigate to Setup | Quick find search for Approval Processes and click the result. 
2. Find the Approval Process in question.
3. Deactivate this Approval Process.
4. Use the "Clone" button (from the Approval Process detail page) to create a new Approval Process.
5. Create or modify the Approval steps as desired.

Note: Active Approval Process cannot be cloned and needs to be deactivated first as described above. If you don't see "Clone" button, make sure it's deactivated first. This is a technical design to ensure the data integrity to prevent unintended changes to the in-flight approval requests.  

Note:

• The records that were submitted with the old approval process will not reflect the changes done to the new approval process, they would have to be submitted for approval again using the new approval process.