Custom-mode-menu is a variable defined in `cus-edit.el'.
Its value is shown below.

Menu used in customization buffers.


(keymap "Custom" (Customize menu-item "Customize" nil :filter #[257 "\302\301!\300\"\207" ["Customize" (lambda (&rest junk) (let ((menu (custom-menu-create 'customize))) (if (consp menu) (cdr menu) menu))) easy-menu-filter-return] 4 "\n\n(fn MENU)"]) (\ Apply\ menu-item " Apply " Custom-set :help "Apply settings (for the current session only).") (\ Apply\ and\ Save\ menu-item " Apply and Save " Custom-save :enable 'nil :help "Apply settings and save for future sessions.") (\ Undo\ Edits\ menu-item " Undo Edits " Custom-reset-current :help "Restore customization buffer to reflect existing settings.") (\ Reset\ Customizations\ menu-item " Reset Customizations " Custom-reset-saved :help "Undo any settings applied only for the current session.") (\ Erase\ Customizations\ menu-item " Erase Customizations " Custom-reset-standard :enable 'nil :help "Un-customize settings in this and future sessions.") (\ Help\ for\ Customize\ menu-item " Help for Customize " Custom-help :help "Get help for using Customize.") (\ Exit\ menu-item " Exit " Custom-buffer-done :help "Exit Customize."))