The button spacing flags determine the vertical and/or horizontal spacing between a series of buttons on a converted screen. The flags are only effective on buttons with the "auto arrange" property set to true. The spacing is specified in pixels and accounts for the button height or width in addition to the space between the buttons. By default, buttons are arranged horizontally on window formats and vertically on regular non-window formats. (This can be overridden by the Horizontal Auto Arrange option.)
Where do you save this configuration option? Here.