REQUEST OPTION 1:
Add a second Modified Date field that would get updated whenever any of the item's descendants are modified.
REQUEST OPTION 2:
Similar to the Due Date field's "Automatic Calculation" toggle, on the Modified Date field allow a toggle between date item was modified, and date that it or any of its descendants were modified.
USE CASE:
We would like to list projects, grouped by when anything in them was modified, to show what is being worked on.
Thank you.