[Karellen]

I meant how does Kodi know what to do with it.

Its all coded. You can press the Code button at the top of the forum to see code. I am pretty sure it is simply available for Skins to call upon. Can't give you a technical answer to your question though.

Another method is Smart Playlists. If you look at the available rules see if you can hijack one of them to use for a sort order. First thing that came to mind for me was moving the MCU movies to their own Source. Ensure they are in Movie Folders, then adjust the file name to something like MCU=12 Thor (xxxx) Make sure you have enabled the setting Movies are in their own Movie Folders (or similar wording) in the Add Source settings.

Create your rules on Path and Filename and see if that works.