Pressing this button will save the current options selections as global defaults. It will also save the current dimensions settings for board types (Material Type / Thickness) on the lumber tab.

Being saved globally means when you run MapBoards for the first time on any model the options will be initialized with these values and matching boards types will be intialized with these dimensions. It will also persist when version updates are installed.

Be aware that options and board dimensions are saved locally to the model and when you rerun MapBoard the local settings will override the global settings.