Once all changes have been recorded on the "Engineering Change Request" screen, the document can be Released or sent for Approval, depending on the Approval Workflow for Engineering change has been setup.
If Approval is Enabled then the Release process can only happen once all Approval Entries have been approved by the relevant people.
No changes will be possible when the Status is set to Released of Pending Approval.
After the "Engineering Change Request" is released, it is possible to register the changes in the system, which will perform the updates within Business Central and also create an "Engineering Change Order" document to keep a historical log of the changes for audit and compliance purposes, as detailed here.