According to the old blog I am using the mass operation feature setting classification types.
How to Quickly Set Classification Types for Tables in Oracle SQL Developer Data Modeler (0 Bytes)Summary of problem: The mass assignment works, the mass removal not.
By miss clicking I assigned to many tables for a specific classification type.
The issue I found is that the reverse dialog removing tables from a specific Classification type is not saving the changes.
The changes are shown correctly, but saving the Model does not save the changes from this dialog.
Closing the Model, opening it again the tables have again the additional classification types.
Workaround: Remove the classification types one by one via the table properties dialog.