In a resource scheduler (extender) you can display a tooltip on an appointment, see image below (red box).

The tooltip is called by the extender from a column with a hard copy of, in my example, all fields of the appoinment. Since this field changes with every change of an appointment, the default does not seem like a good place to me. It seems to me that you want to generate this field once just before you save the data. Does anyone know the right place for this action?