horizontal-scroll-bar-mode

horizontal-scroll-bar-mode is a variable defined in `scroll-bar.el'.
Its value is

nil

Documentation:
Non-nil if Horizontal-Scroll-Bar mode is enabled.
See the command `horizontal-scroll-bar-mode' for a description of this minor mode.
Setting this variable directly does not take effect;
either customize it (see the info node `Easy Customization')
or call the function `horizontal-scroll-bar-mode'.

You can customize this variable.