KeepThatInventoryOpen

How it works: When opening an inventory, the client doesn't send a data packet to the server. However, when closing the inventory, such a packet is sent. This system behavior prevents using the crafting grid as additional storage space.

Store items in the crafting grid

KeepThatInventoryOpen is a client-side mod that prevents sending the inventory close packet. This allows you to store items in the crafting grid and cursor slot. But be careful: these items will be thrown out of the inventory when rejoining the world or server.

Use at your own risk. Some servers may consider this an unfair advantage.