I’ve added support for multiple captures of the Name and Ext groups in the Title grouping regex. For example,
(?<Name>.+?)-(?<Name>.+?)(?<Ext>\..+) will create the MainWindow name from the Main-Window.xaml tab. (?<Ext>Test)(?<Name>.+?)(?<Ext>\..+) will create the Test.xaml extension from the TestWindow.xaml. You can use as many separate Name and Ext groups as you need, the resulting string will be concatenated from all captures. It allows you to capture multiple parts of the original tab title as the name or extension. Technically I just switched to the built-in Group.Captures .NET regex feature.
Download link: Tabs Studio v3.1.5.
Update: Connell Watkins shared his use of multiple captures to group lots of similar files.
Tabs Studio Blog (organizing Visual Studio document tabs) 