Aside from the main 3D view there are specialised windows for different elements of the level and route. These can be rearranged and dragged outside of the main view if desired.
Cameras and Sinks (underwater currents) share a data structure in the level so they share a window.
Lists items and their properties.
Lists lights and their properties.
Shows the currently loaded plugins.
Lists room and their properties and contents.
Used to manage the current speedrun route.
Browse static meshes and room sprites (in earlier games).
Shows the texture tiles present in the level.
Lists triggers and their properties.
The main 3D view.
Accessed through the level info section of the Viewer.