Add a Custom Attribute to the General External Link Field in Sitecore I have a requirement where I want to add a custom attribute on the External Link popup just like the below image: Below are the steps which we need to done: Core DB: Go to in core DB Go to this location “/sitecore/system/Field types/Link Types/General Link/Menu/External link” In a message field by default value is “contentlink:externallink(id=$Target)” which we need to update with this “contentlink:externallinkextend(id=$Target)” Now click on General Link and update the “Control” field with this “content:ExtendLinks” Create New Message Handler using Sitecore; using Sitecore.Diagnostics; using Sitecore.Shell.Applications.ContentEditor; using Sitecore.Text; using Sitecore.Web.UI.Sheer; namespace SampleProject.Services { public class ExtendLinks: Link { public override void HandleMessage(Message message) { Assert.ArgumentNotNull((object)message, nameof(mess