How to fixed left menu dropdown in active admin

 JS: app/assets/javascripts/active_admin.js

$(document).ready(function() {

  $(".menu_item.current").addClass("open");

});

----------------------------------------------------

CSS: app/assets/stylesheets/active_admin.scss

.header #tabs li.has_nested.open > a:nth-child(1)::after{

  content: "\f0de" !important; #this is open

}

.header #tabs li.has_nested > a:nth-child(1)::after{

  content: "\f0dd" !important; #this is close

}

.header #tabs li.has_nested.open > ul{

  display: block !important;

}

.header #tabs li.has_nested > ul{

  display: none !important;

}