Frequently, you will receive a new revision of a drawing from a customer. In 1factory, the rule is that Each Part Number and Revision combination requires a new QC Plan. So a drawing revision change will require a new QC Plan.
If you created the QC Plan for the old revision from a drawing, you can use the "new revision" functionality (next to "from a pdf drawing"), select the old revision, enter the new part number and revision, and upload the new drawing.
1factory will transfer all the balloons from the old drawing to the new drawing and create a new QC Plan. You can then edit the features that have changed.
If you created the QC Plan from scratch or from an xlsx upload, you can use the Clone plan to create a copy of the plan with the new Part Number and Revision, and then edit the features that have changed.