Based on my early experience, Sets could emerge as the marquee new feature in Redstone 5.

As you may recall, Microsoft originally hoped to include Sets in Windows 10 version 1803 (Redstone 4), but the feature as originally implemented was too limited—it didn’t even support desktop applications—so it was pushed back to RS5.

Unfortunately, those who are currently testing RS5 may or may not see Sets because Microsoft is doing A/B testing, which is a nonsensical concept in this context. The good news? Rafael has written a utility that will enable Sets if you’re not seeing the feature in your RS5-based PCs.

Visually, Sets is a bit jarring at first: It adds a tab and a Microsoft Edge-like “Previous tabs” button to Store apps and some desktop application windows. It’s not quite as awkward-looking at it was in the RS4 implementation, but it’s still different enough from previous Windows 10 versions that my eyes keep getting distracted by the extra UI. That said, it doesn’t look unnatural or out of place for the most part, and I suspect I will simply get used to it.

On the downside, desktop application compatibility is mixed. MarkdownPad 2 inexplicably supports Sets—which is goofy, since this app has its own document-based tabs—but some other desktop applications I use, like Microsoft Paint, do not. Google Chrome doesn’t support Sets, but web apps I save to the desktop with Chrome, like Google Inbox and Google Calendar, do. (That’s weird.) And my version of Office 2016 doesn’t support Sets either, but I believe I can fix that by getting this PC on Office Insider. I will do that.

So what happens when you select the “New tab” button (or type CTRL + WINKEY + T) in a Sets-capable window? Curiously, it opens a new Microsoft Edge tab, just as it would in Microsoft’s web browser. I’m not quite sure I understand that choice. And I don’t see a way to configure it to work otherwise. (I could see some hoping that it might basically add tabbing to apps that don’t natively support it.) It’s a bit goofy to open a new tab from the Chrome-based Inbox app window and get an Edge tab.

(Oddly, File Explorer does let you open a new File Explorer tab by typing WINKEY + T. But I’ve not yet found any other apps that work like that.)

You’re not limited to using the New tab button, of course: You can also drag a Sets-capable window into another and create a tabbed set that way, too. This works as I expected and seems to not suffer from the overly-sensitive grouping functionality seen in Stardock’s Groupy utility.

As the “Previous tabs” button suggests, tabbed sets will be remembered so you can call them up again later. This is a useful feature in Microsoft Edge, where each tab is a website. But it’s also very useful for apps and other windows. And it addresses a key limitation in virtual desktops, which have no way to save state like that.

Like any proper productivity feature, Sets will reward those who investigate this feature’s handful of useful options. These are found, logically enough, in Settings > System > Multitasking under the new Sets heading.

There are three options.

You can determine whether apps and (Edge-based) websites open new windows automatically in a new tab (the default) or window. I still use the Skype desktop application, and the default behavior short circuits Skype’s multi-window UI, which is one of the reasons I still use this version of the app. (New windows now open in tabs.)

You can also determine whether tabs appear individually in ALT + TAB (which wasn’t the case before with Edge tabs, but is now the default) or not.

And you can create a list of apps that will not work with Sets. This option is smart, but I’m curious if the list will sync with your online account. It should. In any event, adding Skype to the list solved my multi-window problem.

It’s early days, of course, and I’m sure there’s more to learn about Sets, and that Microsoft will be adding new features and tweaking how things work. But this looks solid to me: Sets is a nice antidote to the nonsense features Microsoft added in previous Windows 10 versions.