The only way I've found to do this is to create a separate item in the calendar that displays the parent tasks instead of the child using this selection menu.
Our calendars are either built around one person, one team, or one project. The project ones tend to look like this:
They're all the same project, but different elements.
However, if this isn't what you're looking for there is the custom option under the task labels options I screenshot above. I'm not familiar with how to really mess with that and would love any additional insight anyone has!
