There are no Wikidata items for the various components of the Morris Canal. The few streets or other objects named after locks or planes have a more specific name:etymology but the same name:etymology:wikidata as you have noticed.

Consider the following:
"There is not always a 1-to-1 mapping between OSM and Wikidata. A Wikidata item may refer to several different OSM database objects, for example: a (boundary=administrative) municipality, place=neighborhood, place=city, and place=island might have the same name but be mapped differently in OSM. In this case consider splitting the Wikidata item (or ask for help if you are not sure how to do this).

Some Wikidata items represent features that are mapped as a series of several objects in OSM (e.g. long streets, streams). In such cases, the Wikidata item can be linked to from an appropriate OSM relation."

From what I understand, the tagging scheme I chose is not incorrect but could be improved with a hierarchy of new wikidata items for the several canal components.