With Frontend Submissions installed and activated, the number of columns can be set programmatically for the single vendor page.
/**
* Frontend Submissions: Set the number of columns for the single vendor page (Default is 2).
*
* @return int $columns The number of columns to display.
*/
function themedd_snippet_edd_fes_single_vendor_page_columns( $columns ) {
$columns = 3;
return $columns;
}
add_filter( 'themedd_edd_fes_single_vendor_page_columns', 'themedd_snippet_edd_fes_single_vendor_page_columns', 10, 1 );