Bootstrap:如何在Dropdown 4和Dropdown 5中打开左侧的所有子菜单？

<div class="dropdown">
  <button class="btn btn-secondary dropdown-toggle" type="button" id="dropdownMenuButton" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
    菜单
  </button>
  <div class="dropdown-menu" aria-labelledby="dropdownMenuButton">
    <a class="dropdown-item" href="#">子菜单1</a>
    <a class="dropdown-item" href="#">子菜单2</a>
    <a class="dropdown-item" href="#">子菜单3</a>
    <div class="dropdown-divider"></div>
    <a class="dropdown-item" href="#">子菜单4</a>
  </div>
</div>

.dropdown-menu .dropdown-submenu {
  position: static;
}

.dropdown-menu .dropdown-submenu .dropdown-menu {
  display: none;
}

.dropdown-menu .dropdown-submenu:hover > .dropdown-menu {
  display: block;
}

.dropdown-menu .dropdown-menu {
  display: none;
}

.dropdown-menu .show .dropdown-menu {
  display: block;
}

$('.dropdown-menu a.dropdown-toggle').on('mouseover', function(e) {
  if (!$(this).next().hasClass('show')) {
    $(this).parents('.dropdown-menu').first().find('.show').removeClass('show');
  }
  var $subMenu = $(this).next('.dropdown-menu');
  $subMenu.toggleClass('show');
  $(this).parents('li.nav-item.dropdown.show').on('hidden.bs.dropdown', function(e) {
    $('.dropdown-submenu .show').removeClass('show');
  });
  return false;
});

$('.dropdown-menu a.dropdown-toggle').on('click', function(e) {
  if (!$(this).next().hasClass('show')) {
    $(this).parents('.dropdown-menu').first().find('.show').removeClass('show');
  }
  var $subMenu = $(this).next('.dropdown-menu');
  $subMenu.toggleClass('show');
  $(this).parents('li.nav-item.dropdown.show').on('hidden.bs.dropdown', function(e) {
    $('.dropdown-submenu .show').removeClass('show');
  });
  return false;
});