With Redstone 5, Microsoft brings back its Sets tabbed interface to Windows 10. Sets allows you to use tabs to group apps together within a single window. Not only can you add UWP apps to a Set, but you can add some Win32 apps (like Notepad and File Explorer) as well as Office apps, too.
Sets allows you to drag-and-drop and rearrange tabs, and you have the option of setting the Alt+TAB command to flip between tabs and groups of windows. Alt+TAB now optionally switches between individually opened Edge tabs, too.