custom-reset-button-menu

custom-reset-button-menu is a variable defined in `cus-edit.el'.
Its value is

t

Documentation:
If non-nil, only show a single reset button in customize buffers.
This button will have a menu with all three reset operations.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.3 of Emacs.