3 3D Window
The button in Home tab and Windows->Open->3D Window... command from main menu invoke 3D Window, also called 3D View window.
The 3D Window user interface contains main interface elements in a form of Toolbars and Menu.
The 3D Window is of View type window. It allows project visualisation but does not allow any kind of project editing.
Depending on the circuit type, there are different ways for displaying the project: