On the Load Custom UI Scheme dialog, you specify the base file name of the custom UI scheme you want to load. You can select any type of UI scheme file from the dialog, and 3ds Max will load any other type of UI scheme files with the same base file name.
Use the Files of type drop-down list to search for other types of customization files. The default is .cui, but you can also search for .clr, .mnu, .kbd, .qop, and .ui files. When you choose a filename, all files with that base file name are loaded.