blockly-app/assets/blockly/blocks/blocks_data.json

{
    "categories": {
        "test": {
            "categoryName": "Test blocks",
            "description": "Test blocks to demonstrate this feature.",
            "languages": ["en", "es"],
            "toolboxName": "Test",
            "toolbox": [
                "<category>",
                "  <block type=\"ardublockly_name_top\"></block>",
                "</category>"
            ]
        }
    }
}