Thanks for pointing out the Dashboard Date Drill. That does look helpful!
Yes, for pivot tables I was thinking similar to Excel with the boxes that look like this [-] for “opening” and “closing” the different levels of detail. I’m not sure how it works in Excel, but for our use case it would be nice if you didn’t have to click on every single month see the day-level details. It would be great to have one click to expand to the day-level or collapse to the month-level.