Rows and columns which reference the same item
You cannot make a distinction between two rows or columns which reference the same item. As a result, the local enhancements are assigned to the first item found when the schedules are merged.
Example
Sales figures are spread by country. The user then adds the Sales figures at a different part of the schedule, and spreads them by product this time. When the schedules are merged, the line item details will only be taken into account for the second set of Sales figures added, not the first.