It would be extremely useful to add the option to expand/collapse all subitems on a board at once. It’s been my experience that sometimes tasks are overlooked which has resulted in missed deadlines. As a bit of additional information, we consistently add temporary guests to some of our boards who are assigned tasks, and even though we explain that they need to look for Subitems they are sometimes missed anyway.
This would also be extremely useful to our internal users (i.e. those who manage the boards) to be able to expand all subitems at once as it would provide much greater ease to view everything at once instead of having to click each one - especially when we are exporting to Excel. I have spoken with many of our other internal users and everyone agrees that it would be super helpful to add this option.