Mac secondary keyboard to execute shortcut only

karabiner.json

// after trying to build my own shortcut keyboard with arduino. 
// I realize that it would be time and cost effective to re-use a spare mechanical keyboard to execute my shortcut.
// Karabiner offers a simple easy solution even it's a bit of twist.
//
// source: https://stackoverflow.com/questions/63194740/karabiner-elements-map-a-key-to-a-combination-keys
//
// edit: ~/.config/karabiner/karabiner.json
//
// Remap the secondary keyboard key d to command + d -> duplicate line in the VS code command palette
"devices": [
 {
                    "disable_built_in_keyboard_if_exists": false,
                    "fn_function_keys": [],
                    "identifiers": {
                        "is_keyboard": true,
                        "is_pointing_device": false,
                        "product_id": 36,
                        "vendor_id": 1241
                    },
                    "ignore": false,
                    "manipulate_caps_lock_led": true,
                    "simple_modifications": [
                        {
                            "from": {
                                "key_code": "d"
                            },
                            "to": [
                                {
                                    "key_code": "d",
                                    "modifiers": "command"
                                }
                            ]
                        }
                    ],
                    "treat_as_built_in_keyboard": false
                },