This is by design. The ToDo-view is always limited to 20 tasks. If you would like to see all tasks (through paging), you need to use the task list view, and not the ToDo view.
Hello Petra, What are the challenges in achieving more than 20 task in the ToDO view. There is no literal message to our business that only 20 task would be viewed in TODo view
Customer support service by UserEcho