Error when trying to add user defined JavaFX module?

I posted this morning querying how to run multiple modules in a single project, and although the link provided did help me get closer to a resolution, my ticket was marked answered but the issue is not resolved and I am now receiving the error as per the attached screenshot: 

The original post is here:

Multiple JavaFX projects in project view?

Please merge my tickets marking the it unanswered, or at least leave one not marked answered until I confirm the issue is resolved.