Hello I have issue with Umbraco back office. It doesn't render level 2 child nodes in the custom section tree. I have no issue to make issue to make level 1 child node as root node for level 2 child nodes.

  [Tree("Test", "TestTree", TreeTitle = "Dashboard", TreeGroup = "Test", SortOrder = 1)]
    [PluginController("Test")]
 protected override TreeNodeCollection GetTreeNodes(string id, FormDataCollection queryStrings)

    {
        if (id == Constants.System.Root.ToInvariantString())
        {
            Dictionary<int, string> amberMenu = new Dictionary<int, string>();

            testMenu.Add(1, "Test");

            var nodes = new TreeNodeCollection();

            foreach (var menu in amberMenu)
            {
                var node = CreateTreeNode(menu.Key.ToString(), "-1", queryStrings, menu.Value, "icon-presentation", true);
                var nodeTest = CreateTreeNode("1", "1", queryStrings, "Warehouses", "icon-presentation", false, "Test/testTree/index");
                nodes.Add(node);
            }

            return nodes;
        }

        throw new NotSupportedException();
        return new TreeNodeCollection();
    }

    protected override MenuItemCollection GetMenuForNode(string id, FormDataCollection queryStrings)
    {
        var menu = new MenuItemCollection();

        if (id == Constants.System.Root.ToInvariantString())
        {
            menu.Items.Add(new CreateChildEntity(Services.TextService));
            menu.Items.Add(new RefreshNode(Services.TextService, true));
           return menu;
        }
        return menu;

        return null;
    }

    protected override TreeNode CreateRootNode(FormDataCollection queryStrings)
    {
        var root = base.CreateRootNode(queryStrings);

        root.Icon = "icon-hearts";
        root.HasChildren = true;
        root.MenuUrl = null;

        return root;
    }
}