Changing mouse motion to scroll when the left mouse button is pressed in UHK Trackpoint module

uhk.json

{
  "title": "Configurations for UHK Trackpoint module",
  "rules": [
    {
      "description": "pointing_button(button1) to enable mouse_motion_to_scroll",
      "manipulators": [
        {
          "type": "basic",
          "from": {
            "pointing_button": "button1",
            "modifiers": {
              "optional": ["any"]
            }
          },
          "parameters": {
            "basic.to_if_held_down_threshold_milliseconds": 100
          },
          "to": [
            {
              "pointing_button": "button1"
            }
          ],
          "to_if_held_down": [
            {
              "set_variable": {
                "name": "enable_mouse_motion_to_scroll",
                "value": 1
              }
            }
          ],
          "to_after_key_up": [
            {
              "set_variable": {
                "name": "enable_mouse_motion_to_scroll",
                "value": 0
              }
            }
          ]
        },
        {
          "type": "mouse_motion_to_scroll",
          "from": {
            "modifiers": {
              "optional": ["any"]
            }
          },
          "conditions": [
            {
              "type": "variable_if",
              "name": "enable_mouse_motion_to_scroll",
              "value": 1
            }
          ],
          "options": {
            "speed_multiplier": 0.5
          }
        }
      ]
    }
  ]
}