[Karabiner][V13] left_shift twice to toggle between Control <=> Command - https://dailylime.kr/898/

control_command_switch.json

{
  "title": "[V13] left_shift twice to toggle between Control <=> Command",
  "rules": [
    {
      "description": "Press left_shift twice to toggle between Control and Command key. Another key pressed during each left_shift press will be considered as a cancel, and timeout will also considered as cancel.",
      "manipulators": [
        {
          "conditions": [
            {
              "type": "variable_if",
              "name": "left_shift toggled",
              "value": 1
            }
          ],
          "type": "basic",
          "from": {
            "key_code": "left_control",
            "modifiers": {
              "optional": [
                "any"
              ]
            }
          },
          "to": [
            {
              "key_code": "left_command"
            }
          ]
        },
        {
          "conditions": [
            {
              "type": "variable_if",
              "name": "left_shift toggled",
              "value": 3
            }
          ],
          "type": "basic",
          "from": {
            "key_code": "left_control",
            "modifiers": {
              "optional": [
                "any"
              ]
            }
          },
          "to": [
            {
              "key_code": "left_command"
            }
          ]
        },
        {
          "conditions": [
            {
              "type": "variable_if",
              "name": "left_shift toggled",
              "value": 1
            }
          ],
          "type": "basic",
          "from": {
            "key_code": "left_command",
            "modifiers": {
              "optional": [
                "any"
              ]
            }
          },
          "to": [
            {
              "key_code": "left_control"
            }
          ]
        },
        {
          "conditions": [
            {
              "type": "variable_if",
              "name": "left_shift toggled",
              "value": 3
            }
          ],
          "type": "basic",
          "from": {
            "key_code": "left_command",
            "modifiers": {
              "optional": [
                "any"
              ]
            }
          },
          "to": [
            {
              "key_code": "left_control"
            }
          ]
        },
        {
          "conditions": [
            {
              "type": "variable_if",
              "name": "left_shift toggled",
              "value": 0
            }
          ],
          "type": "basic",
          "from": {
            "key_code": "left_shift"
          },
          "to": [
            {
              "key_code": "left_shift"
            }
          ],
          "to_if_alone": [
            {
              "set_variable": {
                "name": "left_shift toggled",
                "value": 2
              }
            }
          ],
          "to_delayed_action": {
            "to_if_invoked": [
              {
                "set_variable": {
                  "name": "left_shift toggled",
                  "value": 0
                }
              }
            ]
          }
        },
        {
          "conditions": [
            {
              "type": "variable_if",
              "name": "left_shift toggled",
              "value": 2
            }
          ],
          "type": "basic",
          "from": {
            "key_code": "left_shift"
          },
          "to": [
            {
              "set_variable": {
                "name": "left_shift toggled",
                "value": 0
              }
            }
          ],
          "to_if_alone": [
            {
              "set_variable": {
                "name": "left_shift toggled",
                "value": 1
              }
            }
          ]
        },
        {
          "conditions": [
            {
              "type": "variable_if",
              "name": "left_shift toggled",
              "value": 1
            }
          ],
          "type": "basic",
          "from": {
            "key_code": "left_shift"
          },
          "to": [
            {
              "key_code": "left_shift"
            }
          ],
          "to_if_alone": [
            {
              "set_variable": {
                "name": "left_shift toggled",
                "value": 3
              }
            }
          ],
          "to_delayed_action": {
            "to_if_invoked": [
              {
                "set_variable": {
                  "name": "left_shift toggled",
                  "value": 1
                }
              }
            ]
          }
        },
        {
          "conditions": [
            {
              "type": "variable_if",
              "name": "left_shift toggled",
              "value": 3
            }
          ],
          "type": "basic",
          "from": {
            "key_code": "left_shift"
          },
          "to": [
            {
              "set_variable": {
                "name": "left_shift toggled",
                "value": 1
              }
            }
          ],
          "to_if_alone": [
            {
              "set_variable": {
                "name": "left_shift toggled",
                "value": 0
              }
            }
          ]
        }
      ]
    }
  ]
}

L7~L98: Swaps Control <-> Command depends on variable
L99~L228: Toggles variable on key pressed twice