If it's the second screenshot from gabe's post, that you have in mind, this functionality is enabled when you select the "Allow multiple URLs
for this page" option form the page's Title and Properties menu. It allows you to keep a list of all the additional URLs you have specified for that particular page. In addition, you can always access the Urls collection of the particular PageNode, and manage it programatically, just have in mind that you'll need to set the RedirectToDefault property to true, if you want the programatically added additional URL to redirect your users to the new page.
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items