In a blog post, Microsoft stated:
With it, Windows Insiders can create and send group messages, as well as make group audio and video calls. In the latest experience, you can see up to four video images at once, which comes in handy when you want to witness everyone's reaction to your latest and greatest jokes or chat about the season finale of your favorite show. You can also chat with your group and keep the conversation going via group instant messaging. Have favorite groups? In this release, you can also mark any person or group as a favorite.
The new Skype Windows 10 app update also allows texts to be edited or deleted. Microsoft added that the Windows 10 Mobile version of the Skype app is due for release soon:
The mobile release of the Skype UWP Preview app will bring you features you've asked for—like group calling and more—while leveraging the benefits of the Skype integration into Windows 10 you previously experienced, like a single view of your SMS and Skype conversations. This way you get the best Skype experience possible and you can take it across your Windows devices.