It is documented here on the wiki due to being officially-released content by Mojang Studios, even if not present in a final version.
The leftover is a block introduced in Java Edition 20w14∞ that forms the "zones" in the "zones" dimension.
The leftover cannot be obtained as an item even by using the
/give command. The leftover can be placed using commands such as
/setblock, and naturally generates in the "zones" dimension. It cannot be destroyed by tools or explosions.
Leftovers naturally generate in the "zones" in the "zones" dimension, forming areas of danger throughout the overworld-like environment.
The leftover is non-solid, and invisible apart from emitting "Happy Villager" particles. An entity entering it is inflicted by Blindness II and Poison IV for 3 seconds each. It is not possible for other blocks to be placed inside of a leftover, nor can pistons move or destroy it. When an item is thrown into it, it affects the gravity of the item.
|Sound||Subtitles||Source||Description||Resource location||Translation key||Volume||Pitch||Attenuation|
|Block broken||Blocks||Once the block has broken||1.0||0.8||16|
|Block placed||Blocks||When the block is placed||1.0||0.8||16|
|Block breaking||Blocks||While the block is in the process of being broken||0.25||0.5||16|
|None[sound 1]||Entity-Dependent||Falling on the block with fall damage||None[sound 1]||0.5||0.75||16|
|Footsteps||Entity-Dependent||Walking on the block||0.15||1.0||16|
|20w14∞||Added the leftover.|
|3D Shareware v1.34||