Always open all side menu items (groups and sub groups) - xmpie-users/uStore-js GitHub Wiki

By default, a sub-menu item will only be shown if you choose its parent menu item or choose it.

In case you always want to always show all items, then you can add some code to do it.

This JavaScript can be added to the relevant store to achieve this:

<script type="text/javascript">
  $(document).ready(function() {
    $(".rtUL").show();
  });
</script>

The same code can be altered to always show any item, according to its class or ID, by changing the ".rtUL" the following way:
".ClassName"
"#IDName"

For information on how to add JavaScript to your store: How to add JavaScript to a storefront.