Hello,
Could you please be more specific about this feature? If you want only to display a general page in the back end of Kentico then I would recommend you to create a
custom module to separate it from your site. However, you can also create a link to an external page by editing the munu behavior (this will however redirect you to another site) in Properties / Menu / Menu actions. You can also combine the
portal engine and aspx approach to display an external site. Or you could create a module as I mentioned and use the "Target URL" property to link a tab in CMSDesk (however not in the content tree) by adding a module in CMSSiteManager / Development / Modules /
CMS Desk / User Interface / New Element. However, if you want to display it only as a tree node you will have to create a custom aspx page or a web part which would display a site in an iframe. A simple tutorial can be found
here.
Best regards,
Boris Pocatko