Your MONITOR system allows you to create Alternate preparations. An alternate preparation means that you can configure certain terms and conditions for the operation or material rows during preparation. Terms and conditions mean that an operation row or material row should replace the previous row, or that an extra row should be added or deleted, for example for a particular customer or a certain period of time etc. See Different terms for alternate preparation.
In order to use alternate preparations you have to make a selection in the setting Use alternate preparations? under the Preparations heading under the Manufacturing tab in the Settings procedure.
Also read about how manufacturing orders are affected by terms.