[nimish]

The ability to clean the library is nice when there have been several files removed.  However, for those with large libraries, this can take quite some time.
It would be nice to be able to clean a subset of the library.  For example, if you right click on a TV Show, it would be nice to clean the library just for this show, so it would only go through the episodes of that show and remove items that no longer exist.  This could save significant time.

[Hitcher]

Refresh info on the show will do the same thing.

[nimish]

When you refresh info on a TV Show, it scrapes all the episodes again which for a large series can take a long time. 
Whereas when you clean the library, it doesn't scrape the episodes.  It just cleans up files that don't exist anymore.

[Karellen]

Maybe try this... https://forum.kodi.tv/showthread.php?tid=369984

[PatK]

I should also be pretty obvious if you hit a specific video that doesn't play that has been deleted but is still showing up in the cache, there is an option to remove.