I want that cow calendar.

The server certainly should have picked up the change in metadata but I can’t help you with why it didn’t.
I can suggest that you edit the metadata in Jellyfin rather than using external tools and moving items in and out of the library. Just click the three-dot menu for a track or album and choose “Edit metadata”. If it doesn’t pick up changes made from Jellyfin then something is very wrong.

If you can avoid having you server and the media library on separate systems you should. That means buying (or I suppose building, but I wouldn’t recommend it) a NAS with sufficient processing ability to stream / transcode as much as you need, or stuffing a lot of storage into your mini PC.
One of the problems you’ll run into if you use separate systems is that it’s non-trivial to get the server to automatically notice new items in the media library and update to include them. I’m sure there are others.

So this WON’T break the “Jellyfin” Kodi plugin? Just making sure it’s not the same thing as “Jellyfin4Kodi”.

Well that’s a shame. I’m sort of half-assedly using syncthing to backup my photos from my phone to my server, but mostly I rely on immich. I never really got the hang of using syncthing with my phone.

If you didn’t want to click through:

Pixel 9 Pro Fold  
Pixel 9 series  
Pixel 8 series  
Pixel 8a  
Pixel Fold  
Pixel Tablet  
Pixel 7a  
Pixel 7 series  
Pixel 6a  
Pixel 6 series  

The only console I ever spent a lot of time with was the NES, so I’m not at all native to the modern XBox / Play Station controller with its 166 buttons. But I know that some games are best with a controller, so I bought a Steam Controller and an XBox controller. I made it most of the way through Nier Automata with the Steam Controller, but I put the game down for some reason or another. I also gave Hades (what I think was) a good effort, but I never made it out and I stopped caring.
The only game I’ve completed with a controller is Brothers: A Tale of Two Sons, which you really shouldn’t play with m+k, if it’s even possible. I’d never try to play an FPS with a controller.