Fine volume control (g915 tkl volume wheel) adapted from https://ke-complex-modifications.pqrs.org/#fine_volume_control

fvc.json

{
  "title": "Fine volume control (g915 tkl volume wheel)",
  "rules": [
    {
      "description": "Map volume wheel controls to fine volume controls (Option + Shift + Volume)",
      "manipulators": [
        {
          "type": "basic",
          "from": {
            "key_code": "volume_decrement"
          },
          "to": [
            {
              "key_code": "volume_decrement",
              "modifiers": [
                "left_shift",
                "left_option"
              ]
            }
          ]
        },
        {
          "type": "basic",
          "from": {
            "key_code": "volume_decrement",
            "modifiers": {
              "mandatory": [
                "fn"
              ]
            }
          },
          "to": [
            {
              "key_code": "f11",
              "modifiers": [
                "fn"
              ]
            }
          ]
        },
        {
          "type": "basic",
          "from": {
            "key_code": "volume_increment"
          },
          "to": [
            {
              "key_code": "volume_increment",
              "modifiers": [
                "left_shift",
                "left_option"
              ]
            }
          ]
        },
        {
          "type": "basic",
          "from": {
            "key_code": "volume_increment",
            "modifiers": {
              "mandatory": [
                "fn"
              ]
            }
          },
          "to": [
            {
              "key_code": "f12",
              "modifiers": [
                "fn"
              ]
            }
          ]
        }
      ]
    }
  ]
}

https://genesy.github.io/karabiner-complex-rules-generator/#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