Minecraft 15w32a, Minecraft 15w35b, Minecraft 15w45a, Minecraft 16w35a, Minecraft 1.11.2, Minecraft 1.12.1, Minecraft 1.13.1, 1.15.2, 1.16 Pre-release 5, 1.16 Pre-release 7, 1.16, 1.16.1, 1.16.2 Pre-release 1, 1.16.3, 1.16.5, 21w05b, 21w08b, 1.19
Shift-clicking an item which is not an offhand item (like a shield) will never move it to the offhand, even if no other slots are free or the offhand has already the same item.
- Place a chestplate in the chest armor slot
- Will your complete inventory except for the offhand slot with items
- Try to shift-click the chestplate into the offhand slot
→ It does not work
- Set your gamemode to survival
- Put some torches in your offhand slot
- Craft more torches and collect them using shift-click
→ Torches won't stack on the offhand slot but in the inventory
Based on 1.11.2 decompiled using MCP 9.35 rc1
The method net.minecraft.inventory.ContainerPlayer.transferStackInSlot(EntityPlayer, int) only tries to merge items with items in slots up to (excluding) index 45 which is offhand. Therefore the items cannot be moved into the offhand.