The /give and /replaceitem commands are fine if I want to create a new item with a custom attribute, but is there a command to add an attribute to an existing item?
The closest I've gotten to this is adding attributes to an entity representing a dropped item, but the attributes do not carry over to the item once picked up:
/entitydata @e[type=Item,r=1] {AttributeModifiers:[{...}]}
Thanks in advance!