menu-prompting

menu-prompting is a variable defined in `C source code'.
Its value is

t

Documentation:
Non-nil means prompt with menus when appropriate.
This is done when reading from a keymap that has a prompt string,
for elements that have prompt strings.
The menu is displayed on the screen
if X menus were enabled at configuration
time and the previous event was a mouse click prefix key.
Otherwise, menu prompting uses the echo area.

You can customize this variable.