Add Item NBT

Adds a number to a pre-existing number NBT of an Item.

Usage: /additemnbt <player> <slot> <namespace> <key> <amount>

• Player - Player whose inventory is used

• Slot - Slot of Item

• Namespace - Namespace of NBT

• Key - Key of NBT

• Amount - Numerical value to add to NBT

Uses NameSpacedKey