The simple layout hierarchy described in Section 2.3 on page 6 has a number of problems associated with it, all of which revolve around the fact that the task list manager does not yet look very much like a standard Windows application. Although it is a simple design that does not warrant a complicated user interface, the design you have already seen looks more like a dialog box than an application window.
This section shows you how to improve on the basic design, adding a menu bar and replacing the buttons with a proper tool bar. It also shows you how to move the text field into a separate dialog that pops up when you click the Add task button in the tool bar.
From this point on, the interface is defined more formally, using frames. Up to now, the layout hierarchy has been presented informally, and you have used contain to display the layout interactively. This is fine for code that you want to evaluate once only, perhaps using the interactor, but for permanent code, a more rigorous framework is preferable.