As you may recall from Chapter 5, there are three total UI systems that can be used within Unity. Up to this point, the focus of this book has been on Unity UI (uGUI), which can be used to make in-game (aka runtime) UI. However, if you want to make UI that can be viewed in your Editor, you will have to use a different system. The two systems that can be used to create Editor UI are IMGUI, which we will discuss in the next chapter, and the UI Toolkit. However, while IMGUI can only be used to make Editor UI, the UI Toolkit can be used to make both runtime and Editor UI.

Figure 18.1: Comparing the three UI systems

Unity’s goal is to replace the uGUI system entirely with the new UI Toolkit. However, it is still in development and does not have all the functionalities that uGUI does. For example, the UI Toolkit cannot make UI that is positioned in the 3D world, like what we discussed in Chapter 16. It can only make UI that overlays...