Extras are showing fine on my Apple TV 4K.
There’s one limitation with regards to local extras for tv shows where the Apple TV Plex client currently cannot display extras for seasons (extras for the shows themselves and episodes are displaying just fine).
When you write you cannot see them… do you mean they’re not displayed or they fail to play?
As pointed out above… the Apple TV won’t show any season-level extras – only those for the show itself and individual episodes. Plex Web will only show local tv-show extras for the show.
There’s a feature suggestion to update the UI on all clients to support local extras for all tiers of a tv show. That thread also contains a summary of what clients currently support local tv-show extras and for what tiers.
I certainly hope so but I cannot tell for sure.
Plex don’t usually comment on their roadmap.
I’ve seen some users simply moving those season-level extras to the show level (including a season prefix in the file name – e.g. Season 1: Character Dossier - Aram Mojtabai.mkv).
Side note…
Your extra naming is redundant and might be causing some conflicts down the road. If you’re organizing extras in their own folders (here: Scenes), you don’t need to add the extra-type suffix (here: -featurette) – especially if those are conflicting types.
Example 1
Season 01
Scenes
Character Dossiers Aram Mojtabai.mkv
The Blacklist - s01e01 - Pilot.mkv
...
Example 2
Season 01
Character Dossiers Aram Mojtabai-featurette.mkv
The Blacklist - s01e01 - Pilot.mkv