Recently I had to add a Bootstrap modal trigger from a WordPress Menu item, the modal trigger requires an attribute of data-toggle with a value of modal. There is no facility to add this to a Menu Item in a menu in WP Dashboard, however their are 2 solutions on how this can be done.

Their is a filter available to add this nav_menu_link_attributes

add_filter( 'nav_menu_link_attributes', 'filter_function_name', 10, 3 );

function filter_function_name( $atts, $item, $args ) {
    // Manipulate attributes
    return $atts;
}

In the Dashboard add in a Custom Link give it the modal link like href=”#MyModal”

Get the ID in the code using Web Inspector tools, add the ID as a variable, once that ID is matched add in the new attribute and value, in the case below data-toggle and modal

add_filter( 'nav_menu_link_attributes', 'themeprefix_menu_attribute_add', 10, 3 );
function themeprefix_menu_attribute_add( $atts, $item, $args )
{
  // Set the menu ID
  $menu_link = 1215;
  // Conditionally match the ID and add the attribute and value
  if ($item->ID == $menu_link) {
    $atts['data-toggle'] = 'modal';
  }
  //Return the new attribute
  return $atts;
}

 

 jQuery Way

This is also achievable via jQuery

<script>
jQuery(document).ready(function($){
    $(".menu-item-1215").click(function(){
        $("#myModal").modal('show');
    });
});
</script>