How to permanently delete a collection?

[TheDreadPirate]

The collections are dynamically created based on whether they are in a TMDB collection. AFAIK, there is no way to prevent Jellyfin from recreating the collection you renamed or modified. The "lock" feature not working is a known issue.

You could try disabling the library setting I mentioned in my screenshot and instead using the TMDB Boxset plugin to create the collections. It has a scheduled job that you can modify (or disable) so that it isn't willy nilly re-creating collections constantly.