menu.vertical()

m.vertical(true | false | () )
Toggles the menu from a vertical to a horizontal display or vice versa. The effect is the same as shift-clicking the menu's title bar.

Like all functions of this kind, the "vertical()" method can be called in three ways: without a parameter, in which case it returns the actual status of the menu as a boolean, or with one parameter: true or false, in which case it c$sets it. Toggling can be done by
h.vertical ( ! h.vertical() )