Hello Zixuan,
I seemed to find some success by simply dragging the date fields out of my field list and adding them back in... so technically, nothing changed, but somehow it fixed the problem... The Quarters are now nested under the years like they should be and the collapse field works on the year. I don't understand what was wrong because when I dragged the items out and added them back in, I didn't change anything as far as the order, but for whatever reason, it seemed to work. This is how my experience goes with Excel... things don't work and then they do and I never get to know what was wrong or why things changed... but since its working now, I don't think I will bother with the safe mode unless I run into the problem again. Thank you for your suggestions.