Karabiner elements config

karabiner.json

{
  "global": {
    "check_for_updates_on_startup": true,
    "show_in_menu_bar": true,
    "show_profile_name_in_menu_bar": false
  },
  "profiles": [
    {
      "complex_modifications": {
        "parameters": {
          "basic.simultaneous_threshold_milliseconds": 50,
          "basic.to_delayed_action_delay_milliseconds": 500,
          "basic.to_if_alone_timeout_milliseconds": 1000,
          "basic.to_if_held_down_threshold_milliseconds": 500
        },
        "rules": [
          {
            "description": "Shift space",
            "manipulators": [
              {
                "from": {
                  "key_code": "spacebar",
                  "modifiers": {
                    "mandatory": [
                      "left_shift"
                    ],
                    "optional": [
                      "caps_lock"
                    ]
                  }
                },
                "to": [
                  {
                    "key_code": "hyphen"
                  }
                ],
                "type": "basic"
              },
              {
                "from": {
                  "key_code": "spacebar",
                  "modifiers": {
                    "mandatory": [
                      "right_shift"
                    ],
                    "optional": [
                      "caps_lock"
                    ]
                  }
                },
                "to": [
                  {
                    "key_code": "hyphen",
                    "modifiers": [
                      "right_shift"
                    ]
                  }
                ],
                "type": "basic"
              }
            ]
          },
          {
            "description": "Shift to parentheses",
            "manipulators": [
              {
                "from": {
                  "key_code": "left_shift",
                  "modifiers": {
                    "optional": [
                      "caps_lock"
                    ]
                  }
                },
                "to": [
                  {
                    "key_code": "left_shift"
                  }
                ],
                "to_if_alone": [
                  {
                    "key_code": "9",
                    "modifiers": [
                      "left_shift"
                    ]
                  }
                ],
                "type": "basic"
              },
              {
                "from": {
                  "key_code": "right_shift",
                  "modifiers": {
                    "optional": [
                      "caps_lock"
                    ]
                  }
                },
                "to": [
                  {
                    "key_code": "right_shift"
                  }
                ],
                "to_if_alone": [
                  {
                    "key_code": "0",
                    "modifiers": [
                      "right_shift"
                    ]
                  }
                ],
                "type": "basic"
              }
            ]
          },
          {
            "description": "Browser mouse keys",
            "manipulators": [
              {
                "type": "basic",
                "from": {
                  "pointing_button": "button4"
                },
                "to": [
                  {
                    "key_code": "tab",
                    "modifiers": [
                      "left_control"
                    ]
                  }
                ]
              },
              {
                "type": "basic",
                "from": {
                  "pointing_button": "button5"
                },
                "to": [
                  {
                    "key_code": "tab",
                    "modifiers": [
                      "left_control",
                      "left_shift"
                    ]
                  }
                ]
              }
            ]
          }
        ]
      },
      "devices": [
        {
          "disable_built_in_keyboard_if_exists": false,
          "fn_function_keys": [],
          "identifiers": {
            "is_keyboard": true,
            "is_pointing_device": false,
            "product_id": 49285,
            "vendor_id": 1133
          },
          "ignore": false,
          "manipulate_caps_lock_led": false,
          "simple_modifications": []
        },
        {
          "disable_built_in_keyboard_if_exists": false,
          "fn_function_keys": [],
          "identifiers": {
            "is_keyboard": false,
            "is_pointing_device": true,
            "manufacturer": "Logitech",
            "product": "G Pro Gaming Mouse",
            "product_id": 49285,
            "transport": "USB",
            "vendor_id": 1133
          },
          "ignore": false,
          "manipulate_caps_lock_led": false,
          "simple_modifications": []
        }
      ],
      "fn_function_keys": [
        {
          "from": {
            "key_code": "f1"
          },
          "to": {
            "consumer_key_code": "display_brightness_decrement"
          }
        },
        {
          "from": {
            "key_code": "f2"
          },
          "to": {
            "consumer_key_code": "display_brightness_increment"
          }
        },
        {
          "from": {
            "key_code": "f3"
          },
          "to": {
            "key_code": "mission_control"
          }
        },
        {
          "from": {
            "key_code": "f4"
          },
          "to": {
            "key_code": "launchpad"
          }
        },
        {
          "from": {
            "key_code": "f5"
          },
          "to": {
            "key_code": "illumination_decrement"
          }
        },
        {
          "from": {
            "key_code": "f6"
          },
          "to": {
            "key_code": "illumination_increment"
          }
        },
        {
          "from": {
            "key_code": "f7"
          },
          "to": {
            "consumer_key_code": "rewind"
          }
        },
        {
          "from": {
            "key_code": "f8"
          },
          "to": {
            "consumer_key_code": "play_or_pause"
          }
        },
        {
          "from": {
            "key_code": "f9"
          },
          "to": {
            "consumer_key_code": "fastforward"
          }
        },
        {
          "from": {
            "key_code": "f10"
          },
          "to": {
            "consumer_key_code": "mute"
          }
        },
        {
          "from": {
            "key_code": "f11"
          },
          "to": {
            "consumer_key_code": "volume_decrement"
          }
        },
        {
          "from": {
            "key_code": "f12"
          },
          "to": {
            "consumer_key_code": "volume_increment"
          }
        }
      ],
      "name": "Default profile",
      "selected": true,
      "simple_modifications": [],
      "virtual_hid_keyboard": {
        "caps_lock_delay_milliseconds": 0,
        "country_code": 0,
        "keyboard_type": "ansi"
      }
    }
  ]
}

Config file located at ~/.config/karabiner/karabiner.json

Added mappings for mouse buttons 4/5 to next/previous tab respectively. Use to quickly change tabs in Firefox or Chrome browser.