Chained If / else blocks

blocks.js

Blockly.defineBlocksWithJsonArray([  // BEGIN JSON EXTRACT
  {
    "type": "custom_if",
    "message0": "if %1 %2",
    "args0": [
      {
        "type": "input_value",
        "name": "NAME"
      },
      {
        "type": "input_statement",
        "name": "NAME"
      }
    ],
    "previousStatement": null,
    "nextStatement": null,
    "style": "logic_blocks",
    "tooltip": "",
    "helpUrl": ""
  },
  {
    "type": "custom_else_if",
    "message0": "else if %1 %2",
    "args0": [
      {
        "type": "input_value",
        "name": "NAME"
      },
      {
        "type": "input_statement",
        "name": "NAME"
      }
    ],
    "previousStatement": null,
    "nextStatement": null,
    "style": "logic_blocks",
    "tooltip": "",
    "helpUrl": ""
  },
  {
    "type": "custom_else",
    "message0": "else %1 %2",
    "args0": [
      {
        "type": "input_dummy"
      },
      {
        "type": "input_statement",
        "name": "NAME"
      }
    ],
    "previousStatement": null,
    "nextStatement": null,
    "style": "logic_blocks",
    "tooltip": "",
    "helpUrl": ""
  }
]);

toolbox.xml

<xml xmlns="https://developers.google.com/blockly/xml">
  <block type="custom_if">
    <value name="NAME">
      <block type="logic_operation">
        <field name="OP">AND</field>
      </block>
    </value>
    <next>
      <block type="custom_else_if">
        <value name="NAME">
          <block type="logic_operation">
            <field name="OP">AND</field>
          </block>
        </value>
        <next>
          <block type="custom_else"></block>
        </next>
      </block>
    </next>
  </block>
</xml>