Any ideas on why a course cannot be added to the course menu (dashboard)?
This is because those courses are not yet published. An unpublished courses is unavailable to students, and cannot be favorited to show on either the Dashboard or the Courses drop-down list. Once those courses are published, you will be able to star them and make them visible in those locations.
This guide explains this from the student perspective How do I customize my Courses list as a student?
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