kubejs-creative-tab-registry.js

// KubeJS 5 / 1.18.x

const $CreativeTabRegistry = java("dev.architectury.registry.CreativeTabRegistry");

$CreativeTabRegistry.create(
  "test:group", 
  () => Item.of("minecraft:apple")
);

onEvent("item.registry", (event) => {
  event.create("item")
    .group("test.group") // set item group
})

// KubeJS 6+ / 1.19.x

const $CreativeTabRegistry = Java.loadClass("dev.architectury.registry.CreativeTabRegistry");

$CreativeTabRegistry.create(
  Utils.id("test:group"), 
  () => Item.of("minecraft:apple")
);

StartupEvents.registry("minecraft:item", (event) => {
  event.create("item")
    .group("test.group") // set item group
})

// KubeJS 6.1+

StartupEvents.registry("creative_mode_tab", (event) => {
  event.create("test")
    .icon(() => "minecraft:apple")
    .content(() => ["minecraft:apple", "minecraft:golden_apple", "minecraft:enchantment_golden_apple"]);
});