Invisible item frames allow you to add items into the world (like you would with a normal item frame), but without the visibility of the actual item frame item. Preview the image below.
To obtain access, simply progress through the ranks. The specific ranks are follows:
Skeleton: /invisibleitemframes toggle visibility
Phantom: /invisibleitemframes togglemode visibility
Sniffer: /invisibleitemframes toggle glow
Allay: /invisibleitemframes togglemode glow
To remove an invisible item frame, simply punch the item out of the item frame (if it has one), and then punch again to remove the item frame.
