Currently it is possible to define tasks in various pages, however, there is no single place to see them all. This is the reason I use Things in parallel to manage my tasks and double the work.
It would be very useful to create single sheet to show all tasks divided into projects/activities (Notebooks/Sections). Things way of visualization could be a good example. Or maybe you can collaborate which Culture Code on that? (They are pretty late with new version and seems to run out of new concepts)
Another nearby idea is to allow creation of kanban boards for each project/Notebook divided into activities/section. There is plenty of good examples on GitHub like KanbanBoard.
I would say having that all would make Outline center of the universe :0)