As @Krazeh pointed out, that feature never existed in the client app. You can cover some of it using Plex Dash (e.g. changing artwork).
There’s an existing suggestion discussing an option to add more admin features to the player apps.
I suggest you comment/vote in that thread in order to avoid distracting or cannibalizing votes. Unless I’m missing some unique aspect of your suggestion I’ll close this thread as a duplicate.
