Minecraft wiki entry for Development_versions, associated text: Options
Broadcast to LAN can no longer be changed in-game
Graphics
Light is now emitted from below the Nether
Removed the Coral material which served no purpose[2]
Items can now be dragged and dropped within the inventory (expiremental)
Hotbar item count is now at the bottom corner of the selected item (if stackable) and has Java Edition font
Game data is now expressed in JSON files (see here for an example)[3]
Flowers created using bonemeal now depend on the biome