When using modify_tab to add items to an existing tab, simply listing the item ID as a string will append it to the very end of the tab.

However, Recreative allows you to define items as more complex objects to inject them exactly where you want relative to other items!

Syntax

Instead of providing a string (e.g., "minecraft:diamond"), you provide an object with an item field, and optionally an after, before, or components field.

Example: Inserting after an item with Component Data

{
  "action": "modify_tab",
  "tabs": ["minecraft:building_blocks"],
  "add_items": [
    {
      "item": "minecraft:enchanted_book",
      "components": {
        "minecraft:stored_enchantments": {
          "levels": {
            "minecraft:mending": 1
          }
        }
      },
      "after": "minecraft:iron_block"
    }
  ]
}

This places the Mending Book immediately to the right of the Iron Block.

Example: Inserting before an item

{
  "action": "modify_tab",
  "tabs": ["minecraft:building_blocks"],
  "add_items": [
    {
      "item": "minecraft:emerald_block", // Also supports item tags like "#minecraft:logs"
      "before": "minecraft:gold_block"
    }
  ]
}

This shifts the Gold Block to the right to make room for the Emerald Block right before it.

Mixing Simple and Advanced Syntax

You can safely mix standard strings and advanced placement objects in the same add_items list:

"add_items": [
  "minecraft:apple",
  {
    "item": "minecraft:golden_apple",
    "after": "minecraft:apple"
  },
  "minecraft:carrot"
]