I noticed that I am able to filter tasks on the general "Tasks" pane. This is a great feature!
Some ways I was thinking to extend off this feature:
Filter tasks by stacks as well as individual notebooks (i.e. the "school" stack will show all of my school deadlines)
The ability to use labels to sort tasks - for instance, I label a task or a note as "Urgent," then all of the tasks with that label get included in that filter.
Finally, a boolean search. For instance, if I wanted to search in more than one notebook (OR) or exclude keywords (NOT)
Just some thoughts on how to make this great feature even better!