you can duplicate every item by throwing it on the ground and pressing escape until the item is in your inventory and on the ground, then log out and go back in the world and you have doubled the item.
MC-72183
Item Duplicating in Singleplayer
Resolved
Duplicate
0
This is a duplicate of MC-71974. Please be sure to search the bug reports first to see if your issue has already been reported. The majority of tickets are duplicates and sorting through them consumes a lot of time. Thanks for understanding.