Show all Locations on the google maps without assigning them to the map manually.

gistfile1.txt

add_filter('wpgmp_location_criteria', 'wpgmp_location_criteria',1,2 );

function wpgmp_location_criteria($location_criteria,$map) {

  //This will apply for map id 1.
	if( $map->map_id == 1) {
		$location_criteria['show_all_locations'] = true;
  	}
    
	return $location_criteria;

}