karabiner-elements complex rule: left_command to return_or_enter

left_command_to_return_or_enter.json

# put in ~/.config/karabiner/karabiner.json under complex_modifications.rules and restart karabiner-elements

    {
      "description": "Change left_command to return_or_enter if pressed alone (keep as modifier with other keys)",
      "manipulators": [
        {
          "type": "basic",
          "from": {
            "key_code": "left_command",
            "modifiers": {
              "optional": [
                "any"
              ]
            }
          },
          "to": [
            {
              "key_code": "left_command"
            }
          ],
          "to_if_alone": [
            {
              "key_code": "return_or_enter"
            }
          ]
        }
      ]
    }