The Customizations In pane is used to navigate the different user interface elements that are in the loaded customization files.

In this pane, you create and modify user interface elements such as workspaces, toolbars, and menus. Along the top of the pane you will find tools that load partial customization files into the main customization file, save changes to the loaded customization files, and control how you view the loaded customization files.

The tree view is used to create new user interface elements such as toolbars and menus. Once a new user interface element is created, commands can then be added by dragging them from the Command List pane. Along with being able to create user interface elements and add commands to a user interface element, you can change the order in which commands appear on toolbars, menus, and ribbon panels by dragging them up and down.