Adding a new Sheet Metal feature is adding the feature before theFlat Pattern feature. How can a feature be added after the FlatPattern feature?
The new NX12 flat pattern features has the option for "Fix at current timestamp", toggling this option ON and adding a new Sheet Metal feature, that feature will be added after the Flat Pattern feature.
If the flat pattern feature is a Pre-NX12 flat pattern it will nothave the "Fix at current timestamp" option.
The Pre-NX12 Flat Pattern can be converted to the new NX12 FlatPattern feature by using the "Renew Feature" function.
Menu --> Edit --> Feature --> Renew Feature
Refer to the NX12 documentation and What's new in NX12 for more information on Renew Feature.