Minecraft wiki entry for Development_versions, associated text: Version exclusive: A WIP UI-driven layer on top of some of the most common commands.[6]
New command parsing system[7]
Autocomplete works "everywhere", including selector arguments[4]
/tp
Version exclusive: ^ used for coordinates relative to the direction the player is facing.[8]
Version exclusive: facing mode to make the target entity face a specified location/entity upon teleportation.[8]
falling_block is selectable in commands now.[8]
Version exclusive: fishing_hook is also selectable in commands now.[8]
Version exclusive: /detect is now its own separate command[8]