gtk-menu-tool-button-set-arrow-tooltip-markup (button markup)

button -- a gtk-menu-tool-button widget
markup -- a :string with the markup text to be used as tooltip text for button's arrow button

Sets the tooltip markup text to be used as tooltip for the arrow button which pops up the menu. See the function gtk-tool-item-set-tooltip-text for setting a tooltip on the whole menu tool button.