You may not even use it. As powerful as outliners within word processors may be, they are optimized to process words, not to construct outlines. They are bound by the menu choice paradigm, which can be functionally distracting. A dedicated outliner can run rings around a word processor. It turns the outline itself into the interface between the user and program.
Lawyers are familiar with outlines.
Most should intuitively know what to do with the mouse or keyboard in a good outliner. Only a program dedicated to outlining is likely to provide this. Inspiration is such a program, and it takes only 9 megabytes of space. Inspiration is so simple it can be used instantly. Yet it is powerful enough to justify a 348-page manual that is loaded with tips and techniques.