Summary

When you create a Jellyfin library, you usually point a new Library to a folder with your media files in and allow the Jellyfin metadata scraper to examine the file, identify it and then download the metadata to add it to a library.....  but here's a tip ... on any OS worth it's salt, you can have the physical media file in your pyhsical media folder

/media/TV/3 Body Problem/Season 01/3 Body Problem - S01E01 - Countdown WEBRip-720p.mkv'

but, you could also create 

/media/TV/3 Body Problem/Season 01 - Reversed  and create a "link" to the original media file which is a tiny pointer, such as

'linked.mkv --> '3 Body Problem - S01E01 - Countdown WEBRip-720p.mkv'

• When you create the link, it poiunts to the original file, but the link can be named anything
• depending on how you configure your library, it can provide "varied"results 
  • it may scan and find the embedded metadata from the "source" physical media, then look that up
  • it may take just embedded media
  • it may take local NFO data
  • it may not look up at all

so

• the easy part is linking one or two files, get your feet wet and then test a few configurations; 
• always start with a small subzet that "prove" your settings
• then thnk about bulk-naming conventions that work
• then script or automate the file link/rename
• do your inital library scan and then uncheck any changes