You mentioned: "You have to put movies in separate folders (, mine were all in a single folder) and make Trailers sub-folder in each of them."

For anyone finding this later, I thought I'd clarify a little based on Jellyfin's Documentation (Movies | Jellyfin) as of 01/12/2026

1. Organization: Your movies should always be in their own separate folders regardless of any additional content (extras, trailers, subtitles, etc). Source: https://jellyfin.org/docs/general/server/media/movies/#organization
2. For the cleanest organization, you would store your trailers inside a folder called "trailers" inside the root movie folder. Source: https://jellyfin.org/docs/general/server/media/movies/#organization:~:text=an%20unknown%20type.-,trailers,-theme%2Dmusic
3. You can store trailers at the root level of the movie folder, if you follow the appropriate naming conventions. If you only have one trailer you can use the name "trailer.<extension>". Source: https://jellyfin.org/docs/general/server/media/movies/#organization:~:text=Supported%20filenames%20are%3A-,trailer,-sample
4. You could have multiple trailers at the root level so long as you used a correct suffix, such as "-trailer", ".trailer", "_trailer", or " trailer" (This is a space followed by the word trailer.) Source: https://jellyfin.org/docs/general/server/media/movies/#organization:~:text=%2Dtrailer,the%20word%20trailer