[RobinTW]

I don't understand your question, as far as I am concerned the music library does have a remove facility.

But the major reason that Kodi does not have any given feature is because of a lack of volunteer developers with the knowledge, skills, interest and spare time to give freely to the project.

 In Fileview, we can right click a folder to "Scan item to library".  In Library, we can't right click an entry to "Remove" it from library.

I know resources are limited.  However, there is a forum named "Feature Request", so I believe the developers still love users' feedbacks and even requests.  What I just don't understand is why this requested feature is low priority after so many years and requests.