Alternate option for sensor creation: Define calendar/event first

[VynDesign]

I was thinking of creating an integration for counting down to a specific event defined in a specific calendar, but then found this, and I think it's great! But what I would like to be able to do is create an event in any calendar first, and then create the sensor based on that calendar and event, instead of all the events being created in the "Anniversaries" calendar at time of creating the sensor. Going a step further, I would like to be able to create a calendar of different events and have a sensor that simply counts down to whatever may be the next one in that calendar.