The metadata dependency manager is reponsible of this metadata management features:
If you define UDO’s Object in the OWB repository, they can take advantage of all the regular metadata services such as Import, Export, Snapshots, and (probably the most compelling reason to implement UDO’s) Lineage and Impact Analysis (LIA).
Ensure that you choose Show Full Impact in the Menu (Menu > View > Show Full Impact) before the execution of a propagate change