Minecraft wiki entry for Development_versions, associated text: New inventory screen in Creative
Blocks and items are sorted by category, each category in its own tab, the categories are: Building Blocks, Decoration Blocks, Redstone, Transportation, Miscellaneous, Foodstuffs, Tools, Combat, Brewing, and Materials.
The inventory can be searched for specific items: just start typing while in the inventory screen. The search results will be displayed in the Search Items tab.
The player's survival mode inventory is accessible via a tab with the chest as its icon.
Brewed potions will not be included in their own category.
To close the new inventory window, the player must press 'Esc'. Using the default inventory key does not currently work.
Added monster egg to Creative inventory.