How to permanently delete a collection?

[frostbyte]

Thank you for your support. With the "TMDB Boxset" plugin you mentioned all the problems are solved as long "automatically add to collection" is disabled in the movies library, too. The plugin will create duplicated entries on first use, though. So I had to delete the previous collections one by one. But now everything is fine:

• Renaming the auto-generated collections is possible (won't be overwritten anymore).
  
• The boxset creation is based on the "TheMovieDb Box Set Id" entries in the movies, solely. Thus, intended collections (and their recreation) can be avoided by just deleting that id. Super simple to manage.
  
• The fetched metadata is better (previously 90% of my collections didn't have a release date).
  
• The "edit image" > search function for the collections works again.