Custom Model Data
Links to another texture/model; For mc 1.14+
/goop nbt cModelData <player> <slot> [±]<value>[%] [objective]
This edits the NBT data of the item(s) in the specified inventory slots.
Also stores the final total value of custom model data as the score of <player> in the [objective] objective.
Args Breakdown (What everything does)
<Player>
Player whose inventory items' NBT will be edited.
Supports a few vanilla selectors.
[1.6.5] May be an Entity (dropped item) UUID
<Slot>
The slot in the player's inventory in which items will be re-modeled. To read on slots see Inventory Slots.
Examples: mainhand, offhand, chest, feet, any, 0-8, ec*
[±]<value>[%]
The operation to apply to the custom model data of the item. See Plus Minus Percent page for full explanation.
[Objective]
The name of the scoreboard objective that will store (ten times) the final custom model data value.
Tips
You can use +0 as the value to read the custom model data of an item
Then, you may make it take two paths with a MythicMobs skill, one that sometimes edits the CustomModelData into a 'powered' state, and another that reverts this change but also executes cooler particle effects.
Simple Examples:
/goop nbt cModelData cocopad mainhand 4
Changes the custom model data of cocopad's mainhand item to 4
/goop nbt cModelData SugarFlow legs +0 cItem
Sets player SugarFlow's cItem score to the value of custom model data of their equipped leggings. Fails and doesnt do anything if they have no leggings equipped.