Project Management Scheduling (Loom Video)

Let's start with the basics. You want to be able to drag and drop calendar entries on a calendar. I suggest that you make the report a full page rather than embedded in that dashboard so that the calendar entries will be larger and show more data.

You can then drag and drop the calendar entries as long as both the start date and the end date of the appointment is a data entry field and not a formula field. 

So I'm either thinking that you were not aware that you can drag and drop calendar entries and also stretch them bigger or smaller to make them have more or less time or else either the start date or the end date of the appointment is a formula field. Once you have a formula field and you are not able to drag and drop the calendar entries.

If that is the case and yet you walk the end date to default you can use a form rule to auto set the end time of the calendar entry when it is blank and that way it will auto populate but still be able to be dragged and dropped.