Hi @chittesh.pandey - 

If you have a list of which courses are unpublished, rather than check the Learning Plans, you could look within the courses themselves. From Course Management, select your course, then access the Learning Plan tab. That should list out any Learning Plan that the specific course has been assigned to, and allow you to unassign the course. 

I’m not aware of a more automated way to do that unassignment action, unfortunately. I hope this helps.

Hmm, I don’t see an easier way via API for you, the above is probably the fastest approach.