Parsing more complex structure to a variable

Hi.

I am looking for correct way to parse ‘data’ values (need to be nested object) to be able to future parrametrize it.
I tried formatting it as json first - not working.
After couple iterations I got idea of using template node between.
I even managed to produce valid output (or at least I think so)
But in call service node values are doubled.
I am lost.

Call service node except from me something like:

{
"message":"The garage door has been open for 10 minutes.",
"title":"Your Garage Door Friend",
"data":{
 "transparency":"25%",
 "color":"red"
 }
}

This is my current state

[
    {
        "id": "93f8b217c8d567c2",
        "type": "api-call-service",
        "z": "446c2f2ccb426807",
        "name": "",
        "server": "f7ab3ad286dad1b2",
        "version": 5,
        "debugenabled": true,
        "domain": "notify",
        "service": "telewizor_poddasze",
        "areaId": [],
        "deviceId": [],
        "entityId": [],
        "data": "payload",
        "dataType": "jsonata",
        "mergeContext": "",
        "mustacheAltTags": false,
        "outputProperties": [
            {
                "property": "out",
                "propertyType": "msg",
                "value": "",
                "valueType": "data"
            }
        ],
        "queue": "none",
        "x": 650,
        "y": 320,
        "wires": [
            [
                "d9425cc6e65722d7"
            ]
        ]
    },
    {
        "id": "b762a57da83e912f",
        "type": "inject",
        "z": "446c2f2ccb426807",
        "name": "",
        "props": [
            {
                "p": "payload"
            },
            {
                "p": "topic",
                "vt": "str"
            },
            {
                "p": "data.notification.title",
                "v": "Tytuł",
                "vt": "str"
            },
            {
                "p": "data.notification.message",
                "v": "wiadomosc",
                "vt": "str"
            },
            {
                "p": "data.notification.addata",
                "v": "[{\"dataname\":\"color\",\"datavalue\":\"red\"}]",
                "vt": "json"
            }
        ],
        "repeat": "",
        "crontab": "",
        "once": false,
        "onceDelay": 0.1,
        "topic": "",
        "payload": "",
        "payloadType": "date",
        "x": 260,
        "y": 440,
        "wires": [
            [
                "d6bac9da2963fd29"
            ]
        ]
    },
    {
        "id": "d9425cc6e65722d7",
        "type": "debug",
        "z": "446c2f2ccb426807",
        "name": "debug 1",
        "active": true,
        "tosidebar": true,
        "console": false,
        "tostatus": false,
        "complete": "true",
        "targetType": "full",
        "statusVal": "",
        "statusType": "auto",
        "x": 740,
        "y": 520,
        "wires": []
    },
    {
        "id": "d6bac9da2963fd29",
        "type": "template",
        "z": "446c2f2ccb426807",
        "name": "",
        "field": "payload",
        "fieldType": "msg",
        "format": "handlebars",
        "syntax": "mustache",
        "template": "{\n    \"message\":\"{{data.notification.message}}\",\n    \"title\":\"{{data.notification.title}}\",\n    \"data\":{\n      {{#data.notification.addata}}\n        \"{{dataname}}\":\"{{datavalue}}\"\n      {{/data.notification.addata}}\n    }\n}",
        "output": "json",
        "x": 460,
        "y": 440,
        "wires": [
            [
                "d9425cc6e65722d7",
                "93f8b217c8d567c2"
            ]
        ]
    },
    {
        "id": "f7ab3ad286dad1b2",
        "type": "server",
        "name": "Home Assistant",
        "version": 5,
        "addon": false,
        "rejectUnauthorizedCerts": true,
        "ha_boolean": "y|yes|true|on|home|open",
        "connectionDelay": true,
        "cacheJson": true,
        "heartbeat": false,
        "heartbeatInterval": "30",
        "areaSelector": "friendlyName",
        "deviceSelector": "friendlyName",
        "entitySelector": "friendlyName",
        "statusSeparator": ": ",
        "statusYear": "hidden",
        "statusMonth": "short",
        "statusDay": "numeric",
        "statusHourCycle": "default",
        "statusTimeFormat": "h:m",
        "enableGlobalContextStore": false
    }
]