Cannot get extras to appear

[StaticUnit97]

I am trying to add some extras to one of my titles, but no matter how I name the folders or extras, they do not appear in the web player or the desktop media player.

Here is the current structure:

Star Wars Episode V - The Empire Strikes Back (1980)/
├── extras
│   ├── 4K80 24_fast_grain.mkv
│   ├── 4K80 24_fast_none.mkv
│   └── 4K80 source.mkv
├── Star Wars Episode V - The Empire Strikes Back (1980) - 4K83.mkv
└── Star Wars Episode V - The Empire Strikes Back (1980) - D80.mkv

I've tried naming the folder:

• extras
  
• Extras
  
• clips
  
• other
  
• featurettes
  

I've also tried naming the files within this folder, but no matter what, the extras never appear. The permissions across the titles and folders are all the same, too. Is there something I am missing?