Update 1.12/build 2

The first Beta related to Update 1.12 was released on 17 April, 2019. See changelog.

Additions
This is currently still a 'work in progress' feature, and more functionality will be added in future updates.
 * Item instance IDs can now be synchronized between clients and servers.
 * Added auto complete to Command Blocks.
 * Added spawnRadius gamerule
 * Players can specify in their worlds called spawnRadius. The concept was adapted from how Java Edition implemented it. It allows players to specify a number between 0 and 32 to create an allowed area for spawning to take place. So a spawn radius of 27 is a larger circle than a radius of 12. Players then will spawn in a random location in that radius.
 * Enabled content logging on Bedrock Dedicated Server
 * Added a delay option to command blocks
 * A delay can be added to the command block using the new field. The ticks for this delay are Redstone ticks.
 * New Items can be added using Add-Ons
 * Mob events can now be enabled and disabled in world templates
 * Animations and particles can be added without being linked to entities
 * Inventory, Armor, and hand containers can be adapted through scripting
 * Sound effects can now be triggered by animation events
 * Added new executeCommand to the Scripting API
 * Added Scripting events for interaction with items, for example:
 * Item picked up
 * Item dropped
 * Carried item changed
 * Added One-shot animation support, allowing the ability to execute a single animation on an entity
 * Particle emitters can now trigger Scripting Events
 * Updated documentation of Actor Events, to document client-side usage of actor events in resource packs
 * Add Block components now use JSON schemas
 * Created a screen to view content log errors
 * The log screen can be opened using Ctrl+H, or by going to Settings→Profile
 * Added code to allow static validation scripts to be run locally
 * Custom blocks can now be added through Scripting
 * Custom blocks can currently only be added through additional JSON scripting
 * Custom blocks can only be placed with slash commands
 * This section has been heavily edited for summarizing purposes. For the the full changelog see here

Crashes/Performance

 * Fixed several crashes that could occur during gameplay
 * Improved chunk loading performance in multiplayer
 * Further improvements to performance when using selectors with commands
 * Fixed a crash that could occur when switching players on Xbox
 * Cached resource packs no longer cause lag on Nintendo Switch (MCPE-36976)
 * Fixed a crash that could occur when launching the game on some Windows 10 devices
 * Fixed a crash that could occur when certain interactive blocks (e.g. Beds, Chests, Furnaces) are loading in when joining a Realm.
 * Fixed a crash that could occur when engaging in a fight with an Elder Guardian in an Ocean Monument
 * Fixed a crash that could occur when throwing a Trident with Loyalty Loyalty Enchantment
 * Fixed a crash that could sometimes occur when exiting the game

General

 * Player permissions now apply correctly when more than one operator tries to adjust them
 * Arrows that are shot into blocks keep their position when reloading the world
 * Area of Effect clouds no longer try to spawn excessive numbers of particles when time of day is changed (MCPE-39595)
 * Marketplace resource packs are now immediately applied after downloading in the world edit menu (MCPE-33121)
 * The 'Always Day' toggle now correctly animates and shows the correct setting (MCPE-43304)
 * Flowing water is no longer left behind after flowing over string (MCPE-36343)
 * After the fishing_hook is killed by command the player can now cast the hook again without having to right click twice
 * The screen reader prompt no longer appears every time the player adjusts the network settings on Nintendo Switch
 * Removed an unnecessary Xbox Live sign-in notification

Gameplay

 * Marketplace offers page can now show more than 25 items
 * Items that are split between slots in the Villager trade window still count as a total trade amount
 * Blocks can once again be placed on unlit Redstone Ore (MCPE-44305)
 * World settings now sync correctly between different Xbox devices
 * Only players who fought in a Raid see and receive the Hero effect in Realms now
 * Bells now ring when hit with splash and lingering potions
 * Mob spawners now only spawn mobs if the light level is below 7 (MCPE-42427)
 * Cocoa beans now break and drop when pushed by pistons (MCPE-41868)
 * Fixed several related issues with End Gateway portals. These should now teleport the player to the correct safe location when used (MCPE-43176, MCPE-43177, MCPE-19699)
 * Efficiency Pickaxes now break Packed Ice at a faster rate (MCPE-23648)
 * Players that are being healed can still be knocked back by TNT
 * Villagers now keep their job when cured (MCPE-42348)
 * The Grindstone now correctly combines and repairs two damaged items
 * You can now interact with blocks with a charged crossbow on touch devices
 * The Bad Omen effect is now only received when killing a Pillager Captain, and not when dealing non-fatal damage with a bow or damage potion
 * Fixed various scenarios where certain blocks couldn't be placed until the game was restarted

World Generation

 * Fixed a bug on Dedicated servers and Realms which could cause the wrong block types to generate
 * Tweaked the number of job sites in villages

Mobs

 * Cured Villagers now keep their jobs
 * Vindicators can now path correctly over carpet during Raids
 * The Wither no longer plays its spawning animation when reloading a world (MCPE-32415)
 * Mobs will no longer path-find over Brewing Stands
 * Added sound to indicate when a Villager does not want to trade (during a Raid, for instance)
 * Pillager Captains now drop Banners correctly even if the world is reloaded
 * Mobs will now spawn on double slabs (MCPE-30765)
 * Re-added Zombie Villager sounds
 * Mobs now longer get stuck when pathfinding on ladders (MCPE-43034)
 * Added new Wandering Trader sounds
 * Converting a normal Pillager to a Captain with tag commands now displays the banner correctly
 * Evoker no longer moves too fast in "move to village" goal
 * Villagers that are actively trading with players will no longer run and hide if the raid bell rings
 * Clerics can now correctly pathfind to their jobsites

Blocks

 * Scaffolding can no longer be placed on Conduit blocks (this matches Java now)
 * The Bell now swings towards a player when it is hit (matching Java) (MCPE-42469)

Items

 * Dropped items no longer prevent Mine Carts from being placed on Rails
 * Empty glass bottles will now stack correctly when removed from brewing stands (MCPE-42175)
 * Shields no longer appear too bright in item frames (MCPE-41222)
 * Fixed Sea Grass texture brightness (MCPE-34795)
 * Barrel item is now in proper place in creative inventory (MCPE-43946)

Graphical
Noteblock particles now correctly correspond to the notes played
 * Fixed a z-fighting texture issue on some Villager skins
 * Corrected the position of leads on Wolves
 * Fixed missing Zombie Villager skin
 * Farmland now has the correct side and bottom texture (MCPE-42746)
 * Fixed door and trapdoor texture issues (MCPE-43173)
 * Dyed leather horse armour colour no longer effects other horse armour (MCPE-43230)

User Interface
Add-Ons and Script Engine
 * Added controller tooltips for Lectern UI
 * Adjusted Cartography UI to fit Android screens when using Classic UI
 * Villager trading UI no longer opens and closes if the player is standing too far away
 * Added lectern UI controller tooltip
 * Fixed a scripting bug that could cause the player to float
 * Pickblock (middle click) now works correctly on non-vanilla entities that have been added using add-ons (MCPE-38205)
 * ScriptAttackComponent and ScriptCollisionBoxComponent now correctly retrieve updated data
 * Functions ran on a game loop now use an origin which has Game Master permissions, not Owner permissions
 * Added a new constructor parameter to the ServerCommandOrigin so that the Function Manager can create an instance with upgraded permissions.