Example

UNCOMMON:
    type: KEYCRATE
    displayName: '&7[&6Legendary Crate&7]'
    preview:
        enabled: true
    buy:
        enabled: false
        cost: 0
    message:
        onOpen: '&cYou opened a &7[&6Legendary Crate&7]'
        broadcast: ''
    key:
        item: 'TRIPWIRE_HOOK'
        enchantment: '300:1'
        name: '&7[&6Legendary Crate&7] &cKey'
        lore:
            - '&8Right click for amazing rewards!'
    effect:
        onOpenEffects: 'fireworksSpark'
        dormantEffects: 'witchMagic'
    reward:
        minimumRewards: 1
        maximumRewards: 1
        rewards:
            - 'cmd:(/give %player% 265 32), chance:(15), display:(265 32 &b32_Iron_Ingots &aChance:_%chance%_%chance%)'
            - 'cmd:(/give %player% 266 48), chance:(20), display:(266 48 &b48_Gold_Ingots &aChance:_%chance%)'
            - 'cmd:(/give %player% 388 16), chance:(10), display:(388 16 &b16_Emeralds &aChance:_%chance%)'
            - 'cmd:(/give %player% 264 16), chance:(10), display:(264 16 &b16_Diamonds &aChance:_%chance%)'
            - 'cmd:(/give %player% 4 64), chance:(25), display:(4 64 &b64_Cobblestone &aChance:_%chance%)'
            - 'cmd:(/give %player% 3 64), chance:(25), display:(3 64 &b64_Dirt &aChance:_%chance%)'
            - 'cmd:(/give %player% 2 32), chance:(20), display:(2 32 &b32_Grass &aChance:_%chance%)'
            - 'cmd:(/give %player% 88 16), chance:(15), display:(88 16 &b16_Soul_Sand &aChance:_%chance%)'
            - 'cmd:(/give %player% 49 16), chance:(15), display:(49 16 &b16_Obsidian &aChance:_%chance%)'
            - 'cmd:(/give %player% 322 4), chance:(7.5), display:(322 4 &b4_Golden_Apples &aChance:_%chance%)'
            - 'cmd:(/give %player% 322:1 2), chance:(2.5), display:(322:1 2 &b2_Enchanted_Golden_Apples &aChance:_%chance%)'
            - 'cmd:(/give %player% 52:92 1), chance:(10), display:(52 1 &b1_Cow_Spawner &aChance:_%chance%)'
            - 'cmd:(/give %player% 52:93 1), chance:(10), display:(52 1 &b1_Chicken_Spawner &aChance:_%chance%)'
            - 'cmd:(/give %player% 138 1), chance:(5), display:(52 1 &b1_Beacon &aChance:_%chance%)'
            - 'cmd:(/give %player% 52:90 1), chance:(15), display:(52 1 &b1_Pig_Spawner &aChance:_%chance%)'
            - 'cmd:(/give %player% 52:52 1), chance:(5), display:(52 1 &b1_Spider_Spawner &aChance:_%chance%)'
            - 'cmd:(/give %player% 79 32), chance:(20), display:(79 32 &b32_Ice &aChance:_%chance%)'
            - 'cmd:(/give %player% 174 16), chance:(10), display:(174 16 &b16_Packed_Ice &aChance:_%chance%)'