Skype Preview app has received a new update for Windows 10 and Windows 10 mobile. The latest update version is 11.11.105. the latest update added enter support . This is update is only for release preview ring.
Skype Preview app changelog:
added the ability to create a new line when hitting enter on the phone keyboard. The PC version still sends a message.
bug fixes and performance improvement.
You can download the updated app from the given link below.