Hi Kalmer,
No, INVENTORY_ID field was always a data field in Data Type Maintenance but not in Custom Data Maintenance.
Your screen shot looks quite strange as if there is an "illegal" char in the name of a component that makes GUI split the line. Maybe this overwrites the line where Inv ID is displayed. Or maybe it is a side-effect of migration.
You'd rather submit a support ticket and provide a WIP database dump to investigate the issue deeper.
Regards,
Sergiy