Variable: imenu-use-popup-menu
imenu-use-popup-menu is a customizable variable defined in
imenu.el.gz.
Value
on-mouse
Documentation
Use a popup menu rather than a minibuffer prompt.
If nil, always use a minibuffer prompt.
If t, always use a popup menu,
If on-mouse use a popup menu when imenu was invoked with the mouse.
Source Code
;; Defined in /usr/src/emacs/lisp/imenu.el.gz
(defcustom imenu-use-popup-menu 'on-mouse
"Use a popup menu rather than a minibuffer prompt.
If nil, always use a minibuffer prompt.
If t, always use a popup menu,
If `on-mouse' use a popup menu when `imenu' was invoked with the mouse."
:type '(choice (const :tag "On Mouse" on-mouse)
(const :tag "Never" nil)
(other :tag "Always" t)))