[Tree("settings", "favouriteThingsAlias", TreeTitle = "Favourite Things Name", TreeGroup="favouritesGroup", SortOrder=5)]
public class FavouriteThingsTreeController : TreeController
{ }

<language>
  <area alias="treeHeaders">
    <key alias="favouritesGroup">Favourites</key>
  </area>
</language>

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Umbraco.Cms.Core;
using Umbraco.Cms.Core.Actions;
using Umbraco.Cms.Core.Events;
using Umbraco.Cms.Core.Models.Trees;
using Umbraco.Cms.Core.Services;
using Umbraco.Cms.Core.Trees;
using Umbraco.Cms.Web.BackOffice.Trees;
using Umbraco.Extensions;

namespace My.Website.Trees
{
    [Tree("settings", "favouriteThingsAlias", TreeTitle = "Favourite Things Name", TreeGroup = "favouritesGroup", SortOrder = 5)]
    public class FavouriteThingsTreeController : TreeController
    {

        private readonly IMenuItemCollectionFactory _menuItemCollectionFactory;

        public FavouriteThingsTreeController(ILocalizedTextService localizedTextService,
            UmbracoApiControllerTypeCollection umbracoApiControllerTypeCollection,
            IMenuItemCollectionFactory menuItemCollectionFactory,
            IEventAggregator eventAggregator)
            : base(localizedTextService, umbracoApiControllerTypeCollection, eventAggregator)
        {
            _menuItemCollectionFactory = menuItemCollectionFactory ?? throw new ArgumentNullException(nameof(menuItemCollectionFactory));
        }

        protected override ActionResult<TreeNodeCollection> GetTreeNodes(string id, FormCollection queryStrings)
        {
            var nodes = new TreeNodeCollection();

            // check if we're rendering the root node's children
            if (id == Constants.System.Root.ToInvariantString())
            {
                // you can get your custom nodes from anywhere, and they can represent anything...
                Dictionary<int, string> favouriteThings = new Dictionary<int, string>();
                favouriteThings.Add(1, "Raindrops on Roses");
                favouriteThings.Add(2, "Whiskers on Kittens");
                favouriteThings.Add(3, "Skys full of Stars");
                favouriteThings.Add(4, "Warm Woolen Mittens");
                favouriteThings.Add(5, "Cream coloured Unicorns");
                favouriteThings.Add(6, "Schnitzel with Noodles");

                // loop through our favourite things and create a tree item for each one
                foreach (var thing in favouriteThings)
                {
                    // add each node to the tree collection using the base CreateTreeNode method
                    // it has several overloads, using here unique Id of tree item,
                    // -1 is the Id of the parent node to create, eg the root of this tree is -1 by convention
                    // - the querystring collection passed into this route
                    // - the name of the tree node
                    // - css class of icon to display for the node
                    // - and whether the item has child nodes
                    var node = CreateTreeNode(thing.Key.ToString(), "-1", queryStrings, thing.Value, "icon-presentation", false);
                    nodes.Add(node);
                }
            }

            return nodes;
        }

        protected override ActionResult<MenuItemCollection> GetMenuForNode(string id, FormCollection queryStrings)
        {
            // create a Menu Item Collection to return so people can interact with the nodes in your tree
            var menu = _menuItemCollectionFactory.Create();

            if (id == Constants.System.Root.ToInvariantString())
            {
                // root actions, perhaps users can create new items in this tree, or perhaps it's not a content tree, it might be a read only tree, or each node item might represent something entirely different...
                // add your menu item actions or custom ActionMenuItems
                menu.Items.Add(new CreateChildEntity(LocalizedTextService));
                // add refresh menu item (note no dialog)
                menu.Items.Add(new RefreshNode(LocalizedTextService, true));
            }
            else
            {
                // add a delete action to each individual item
                menu.Items.Add<ActionDelete>(LocalizedTextService, true, opensDialog: true);
            }

            return menu;
        }

        protected override ActionResult<TreeNode?> CreateRootNode(FormCollection queryStrings)
        {
            var rootResult = base.CreateRootNode(queryStrings);
            if (!(rootResult.Result is null))
            {
                return rootResult;
            }

            var root = rootResult.Value;

            // set the icon
            root.Icon = "icon-hearts";
            // could be set to false for a custom tree with a single node.
            root.HasChildren = true;
            //url for menu
            root.MenuUrl = null;

            return root;
        }
    }
}

@using Umbraco.Cms.Web.Common.Attributes;

[Tree("settings", "favouriteThingsAlias", TreeTitle = "Favourite Things Name")]
[PluginController("favouriteThings")]
public class FavouriteThingsTreeController : TreeController
{ }

{
    "javascript": [
        "~/App_Plugins/favouriteThings/favouriteThings.resource.js",
        "~/App_Plugins/favouriteThings/backoffice/favouriteThingsAlias/edit.controller.js",
        "~/App_Plugins/favouriteThings/backoffice/favouriteThingsAlias/delete.controller.js"
    ]
}

<div class="umb-dialog umb-pane" ng-controller="Our.Umbraco.FavouriteThings.DeleteController">
    <div class="umb-dialog-body">
        <p class="umb-abstract">
            Are you sure you want to delete this favourite thing: <strong>{{currentNode.name}}</strong> ?
        </p>
        <umb-confirm on-confirm="performDelete" on-cancel="cancel">
        </umb-confirm>
    </div>
</div>

[Tree("settings", "favouritistThingsAlias", TreeTitle = "Favourite Thing", TreeGroup = "favoritesGroup", SortOrder = 5)]
[PluginController("favouriteThing")]
public class FavouritistThingsTreeController : TreeController
{ }

protected override ActionResult<TreeNode> CreateRootNode(FormCollection queryStrings)
{
    var rootResult = base.CreateRootNode(queryStrings);
    if (!(rootResult.Result is null))
    {
        return rootResult;
    }

    var root = rootResult.Value;

    //optionally setting a routepath would allow you to load in a custom UI instead of the usual behaviour for a tree
    root.RoutePath = string.Format("{0}/{1}/{2}", Constants.Applications.Settings, "favouritistThingsAlias", "overview");
    // set the icon
    root.Icon = "icon-hearts";
    // set to false for a custom tree with a single node.
    root.HasChildren = false;
    //url for menu
    root.MenuUrl = null;

    return root;
}

[Tree("settings", "favouritistThingsAlias", IsSingleNodeTree = true, TreeTitle = "Favourite Thing", TreeGroup = "favoritesGroup", SortOrder = 5)]
[PluginController("favouriteThing")]
public class FavouritistThingsTreeController : TreeController
{ }

public void Handle(RootNodeRenderingNotification notification)
{
    // normally you will want to target a specific tree, this can be done by checking the tree alias
    if (notification.TreeAlias.Equals("content"))
    {
        notification.Node.Name = "My new title";
    }
}

using Umbraco.Cms.Core.Security;

public class TreeNotificationHandler :INotificationHandler<TreeNodesRenderingNotification>
{
    private readonly IBackOfficeSecurityAccessor _backOfficeSecurityAccessor;

    public TreeNotificationHandler(IBackOfficeSecurityAccessor backOfficeSecurityAccessor)
    {
        _backOfficeSecurityAccessor = backOfficeSecurityAccessor;
    }

    public void Handle(TreeNodesRenderingNotification notification)
    {
        // this example will filter any content tree node whose node name starts with
        // 'Private', for any user that is in the customUserGroup
        if (notification.TreeAlias.Equals("content") &&
            _backOfficeSecurityAccessor.BackOfficeSecurity.CurrentUser.Groups.Any(f =>
                f.Alias.Equals("customUserGroupAlias")))
        {
            notification.Nodes.RemoveAll(node => node.Name.StartsWith("Private"));
        }
    }
}

using Umbraco.Cms.Core.Events;
using Umbraco.Cms.Core.Notifications;
using Umbraco.Cms.Core.Security;

public class TreeNotificationHandler : INotificationHandler<MenuRenderingNotification>
{
    private readonly IBackOfficeSecurityAccessor _backOfficeSecurityAccessor;

    public TreeNotificationHandler(IBackOfficeSecurityAccessor backOfficeSecurityAccessor)
    {
        _backOfficeSecurityAccessor = backOfficeSecurityAccessor;
    }

    public void Handle(MenuRenderingNotification notification)
    {
        // this example will add a custom menu item for all admin users

        // for all content tree nodes
        if (notification.TreeAlias.Equals("content") &&
            _backOfficeSecurityAccessor.BackOfficeSecurity.CurrentUser.Groups.Any(x =>
                x.Alias.InvariantEquals("admin")))
        {
            // Creates a menu action that will open /umbraco/currentSection/itemAlias.html
            var menuItem = new Umbraco.Cms.Core.Models.Trees.MenuItem("itemAlias", "Item name");

            // optional, if you don't want to follow the naming conventions, but do want to use a angular view
            // you can also use a direct path "../App_Plugins/my/long/url/to/view.html"
            menuItem.AdditionalData.Add("actionView", "my/long/url/to/view.html");

            // sets the icon to icon-wine-glass
            menuItem.Icon = "wine-glass";
            // insert at index 5
            notification.Menu.Items.Insert(5, menuItem);
        }
    }
}

bool canCreateBlogs = false;
var user = _userService.GetByEmail(email);
var userPermissionsForBlog = _userService.GetPermissions(user, blogId);
foreach (var permission in userPermissionsForBlog)
{
    if (permission.AssignedPermissions.Contains("C"))
    {
        canCreateBlogs = true;
    }
}

public interface IAction : IDiscoverable
{
    char Letter {get;}
    bool ShowInNotifier {get;}
    bool CanBePermissionAssigned {get;}
    string Icon {get;}
    string Alias {get;}
    string JsFunctionName {get;}
    /// <summary>
    /// A path to a supporting JavaScript file for the IAction. A script tag will be rendered out with the reference to the  JavaScript file.
    /// </summary>
    string JsSource {get;}
}