NX2312 includes a new Mill Turn Workpiece geometry object that is intended to simplify and streamline the geometry structure of mill turn programming. See the What's New page here:
https://docs.sw.siemens.com/en-US/doc/209349590/PL20230425446868577.whatsnew/xid2250497
The documentation is not clear on what the structure under this parent should look like, specifically what items are allowed to be direct children of the new workpiece.
SolutionIt is recommended that the structure be as shown below, where the MILL_TURN_WORKPIECE contains a milling MCS and a turning MCS as direct children, with appropriate operations under each. Of course, naming convention will certainly vary as per your machine and preferences.
If this is a multi-spindle machine, a separate workpiece structure like this would be created for the subspindle and placed directly under the top level MACHINE_ZERO_MCS object alongside the main spindle workpiece.