But since you can only work with table occurrences, you can't work with data source tables, in this tab of Manage | Database, why is this a problem?
(You should be able to hover the mouse of the arrow in the upper left corner of the Table Occurrence boxes to see their data source table names.)
I thought is would create a table occurrence of the occurrence... and not join correctly.
Ill try it.
If you duplicate a table occurrence, it will refer to the same data source table as the original.
If you use the "new occurrence" button in the far lower left corner, you should get a list of data source tables defined in your DB plus those referenced via external Data source references in other files to select from in order to set up a new occurrence.