If you drag a button to be the first item under a menu in the Project Overview tree structure, it will become the default highlight button for that menu…
From the DVDA Help File:
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A menu's default button is automatically selected when a menu is displayed. In the Project Overview window, a menu's first button is used as the default selected button.
You can override the default button by specifying a destination button in the Button Properties, Media Properties, Music Compilation Properties, and Picture Compilation Properties controls.
You can drag titles in the Project Overview window to change the default button. In the following example, the Band Members button is the default button on the "The Wayfaring Stranger" menu.
my edit: the picture from the help file is not shown here, but it has a menu tree structure, and the first item under the menu is the one listed above...
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Regards,
George