question

So, the answer is yes, but it is a bit complicated. To reference an inventory item you can add the "id" property to the item where the id property is the uuid of an existing Clover inventory item.

{
    "items": [
        {      
            "item": {
                "id": "1WVWNQ58ERXXW"
            }
        },
        {        
            "item": {
                "id": "P50VCQZW8SNVP"
            }
        }
    ]
}

However, you must fill in the rest of the properties (taxRates, prices, etc.). This appears to be an issue in our API and I have created a ticket to have it fixed.