Five outline levels are allowed in a single project.
Plus subprojects, a total of ten levels of outline are allowed - which should be sufficient for most projects.
You will find that most MS project templates organize tasks into 2 to 3 levels of outline.
You will see that QuickPlan is the only application that organizes tasks into REAL task groups and sub-projects. Organizing tasks well into groups and sub-projects makes it easier to understand and track the plan.
If we find that we need to arrange tasks in many levels of outline, there may be a lot of room for us to structure tasks well.
QuickPlan tries to help you with this - we have a best practice article on task structure