While round tripping DDL import and export, the RelationalTable is used to store table unique constraint. The DDL Importer stores the new constraints in the uniqueConstraints collection. However, when saving the model to the BasicTableImpl instance, it actually only looks at the single uniqueConstraint so values are lost.
Dynamic Vdb work has united these fields but retained the getUniqueConstraint() and setUniqueConstraint() methods for backward compatibility with the RelationalTableEditorPanel and ViewTableEditorPanel. These methods are deprecated and the panels should be fixed to support entering multiple unique constraints.