Hi @cma - that is a great question and something I do not think you can do currently. I will send this to the team working on Connector templates as feedback!
In the meantime, one possible workaround might be to add a blank choice in the dropdown? It’s not particularly elegant, and you would need to handle the possibility of an empty variable value in your logic, but maybe it’s a viable workaround for now?
"choices": [
{
"name": "",
"value": ""
},
// ...
}