As your UI is growing more and more complex you will spend quite some time organizing your UI elements in a way that's user-friendly but still leaves enough capabilities to make use of the more advanced features in your AddOns. A great way to achieve this with very little effort is the use of Tabs. Unfortunately the amount of code necessary to generate even a simple tabbing system in WoW is quite large. However, the guys at Blizzard implemented an easy-to-use library that makes the task of handling tabs a whole lot more comfortable.