There have been many times when I would have liked to do this. It should be possible to automatically convert a to do into a calendar entry. And vice versa as well.
Sometimes I create a to do and later, because of a desire to schedule and event within the to do, I wish that I could either permanently, or temporarily, schedule an event in my calendar associated with the to do. The to do has all of my notes associated with it, I'd like to copy those to the calendar entry as well.
When the scheduled event is done, I'd like to convert the scheduled event back to a to do.
I've never understood why a to do is treated so differently versus a calendar entry. Both are events and could be treated similarly as far as I can see.