According to wiki elements from templates should merge together except the ones with value, but this is not the case with NBT tags. This example:
TemplateA:
Hidden: true
NBT:
PublicBukkitValues:
auraskills:item_multipliers:
auraskills:auraskills/foraging: double/50.0
TemplateB:
Hidden: true
NBT:
PublicBukkitValues:
auraskills:item_multipliers:
auraskills:auraskills/farming: double/50.0
Item1:
Id: PAPER
Template: TemplateA,TemplateB
Display: Item 1
Item2:
Id: PAPER
Template: TemplateB,TemplateA
Display: Item 2
Produces following result:
minecraft:paper[custom_name={color: "white", italic: 0b, text: "Item 1"},custom_data={PublicBukkitValues: {"auraskills:item_multipliers": {"auraskills:auraskills/farming": 50.0d}, "mythicmobs:type": "Item1"}}]
minecraft:paper[custom_name={color: "white", italic: 0b, text: "Item 2"},custom_data={PublicBukkitValues: {"auraskills:item_multipliers": {"auraskills:auraskills/foraging": 50.0d}, "mythicmobs:type": "Item2"}}]
Rightmost template overwrites all NBT tags set by other templates. Templates are powerful feature that can allow items to be build by composing them "by feature" - I have created many templates for various things (not being able to repair or scrap item in our custom systems, AuraSkills modifiers/stats or BetonQuest tag for quest item, all of them requires specific tag in NBT/PublicBukkitValues). This allows to compose item by using minimal amount of code:
Chapter2Reward_EtherealReaverSword:
Id: golden_sword
Template: T4_Sword,Unrepairable,Unscrappable,Fighting50
Display: <dark_purple>Rozdzieracz Dusz
Model: 8761000
Lore:
Description: Klinga zrodzona z cierpienia tysiąca rozdartych dusz. Każda z nich pragnie zemsty.
Stats:
- ATTACK_DAMAGE 15 ADDITIVE
- LIFESTEAL_CHANCE 0.2 ADDITIVE
- LIFESTEAL_POWER 0.1 ADDITIVE
This gives such item a baseline of our tier 4 sword (durability, rarity, tooltip style, lore template, augments), marks item as unrepairable and unscrappable (which also adds entry to item lore) and adds 50% fighting skill multiplier (which also adds this stat to lore). It works fine except that unrepairable and unscrappable tags are not present on the item, only fighting multiplier is.