How can i change the hotkey to trigger backslash in in macOS?

i am desperately looking for a way to rebind the backslash symbol on macOS. Preferably something like control + 0. Anything is better than the default keybind. I googled everything that came to my mind related to this matter but I am still lost on how to manage to do it, it looks like this is not as simple as I've thought.

I downloaded karabiner elements but there is no option to define custom keybinds for the backslash symbol.

Does anyone have a solution for this?

Edit:

I've tried to bind my right command key to left shift + left option in the .json file, but it's not working unfortunately. Did i do something wrong? This is the .json file with my custom command:

{
    "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,
                    "mouse_motion_to_scroll.speed": 100
                },
                "rules": []
            },
                "rules": [
                    {
                        "manipulators": [
                            {
                                "description": "Change right command to option+shift.",
                                "from": {
                                    "key_code": "right_command",
                                    "modifiers": {
                                        "optional": [
                                            "any"
                                        ]
                                    }
                                },
                                "to": [
                                    {
                                        "key_code": "right_command",
                                        "modifiers": [
                                            "left_option",
                                            "left_shift"
                                        ]
                                    }
                                ],
                                "type": "basic"
                            }
                        ]
                    }
                ],
            "devices": [
                {
                    "disable_built_in_keyboard_if_exists": false,
                    "fn_function_keys": [],
                    "identifiers": {
                        "is_keyboard": true,
                        "is_pointing_device": false,
                        "product_id": 591,
                        "vendor_id": 1452
                    },
                    "ignore": false,
                    "manipulate_caps_lock_led": true,
                    "simple_modifications": []
                },
                {
                    "disable_built_in_keyboard_if_exists": false,
                    "fn_function_keys": [],
                    "identifiers": {
                        "is_keyboard": true,
                        "is_pointing_device": false,
                        "product_id": 641,
                        "vendor_id": 1452
                    },
                    "ignore": false,
                    "manipulate_caps_lock_led": true,
                    "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": [
                        {
                            "apple_vendor_keyboard_key_code": "mission_control"
                        }
                    ]
                },
                {
                    "from": {
                        "key_code": "f4"
                    },
                    "to": [
                        {
                            "apple_vendor_keyboard_key_code": "spotlight"
                        }
                    ]
                },
                {
                    "from": {
                        "key_code": "f5"
                    },
                    "to": [
                        {
                            "consumer_key_code": "dictation"
                        }
                    ]
                },
                {
                    "from": {
                        "key_code": "f6"
                    },
                    "to": [
                        {
                            "key_code": "f6"
                        }
                    ]
                },
                {
                    "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": "fast_forward"
                        }
                    ]
                },
                {
                    "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",
            "parameters": {
                "delay_milliseconds_before_open_device": 1000
            },
            "selected": true,
            "simple_modifications": [],
            "virtual_hid_keyboard": {
                "country_code": 0,
                "indicate_sticky_modifier_keys_state": true,
                "mouse_key_xy_scale": 100
            }
        }
    ]
}

You can easily put backslash on any main, shift, or option keystroke you want via a custom layout made with Ukelele.

Note also that if you use the layout called German Standard, instead of German, backslash is on Option ß, instead of Option Shift 7.