_tb: Bootstrap activate parent menu - bootstrap-wp-navwalker.php

// Line 87 of 
// If item has_children add atts to a.
if ( $args->has_children && $depth === 0 ) {
	$atts['href'] = ! empty( $item->url ) ? $item->url : '';
	$atts['class']			= 'dropdown-toggle';
	//$atts['data-toggle']   = 'dropdown'; <- This line gets added in theme.js when window width is < 768
	$atts['aria-haspopup']	= 'true';
} else {
  $atts['href'] = ! empty( $item->url ) ? $item->url : '';
}

_tb: style.css

@media (min-width: 768px) {
	.dropdown:hover .dropdown-menu {
    	display: block;
	}
}

_tb: theme.js

jQuery(function($) {
  // Bootstrap menu magic
  $(window).resize(function() {
    if ($(window).width() < 768) {
      $(".dropdown-toggle").attr('data-toggle', 'dropdown');
    } else {
      $(".dropdown-toggle").removeAttr('data-toggle dropdown');
    }
  });
});