Update relations

Hi

I would like to know what is the best way to update data using cipher.

i want to create a visual database for cars and owners of the car. I have an initial set of data like this

{user: javi, {cars: [ferrari, renault, mazda]}

It will insert two different nodes, one for user:

{
"labels": [
"user"
],
"properties": {
"name": "javi"
"cars" : ["ferrari", "renault", "mazda"]
}
}

There will be another node for each of the cars. At this point, everything is fine

Now, i want to reflect that javi has a new car

{user: javi, {cars: [ferrari, renault, mazda, mercedes]}

If i i call the MERGE method, it will create a new node because the data is different, there is a new car, so it doesnt help

What i want to do is to update that existing node and add the new car to the cars properties if node exists.

Is there any easy way to do it?

Thanks