taskbar-groups is described as 'Lightweight application that lets user create and pin groups to the Windows taskbar'. There are three alternatives to taskbar-groups for Windows. The best alternative is Bins. It's not free, so if you're looking for a free alternative, you could try TaskbarDock or ViGlance.
Bins is an utility which allows you to group icons in your Windows Taskbar. - Restore sanity to your Windows taskbar Combine related icons on your Windows 7, 8 or 10 taskbar with Bins. Reduce clutter, and get at your programs quickly.