This update enables the tab list of conversations to be minimized in Microsoft Skype for Business 2015 (Microsoft Lync 2013).
How to get this update
To get this update, install the April 4, 2017, update (KB3178731) for Skype for Business 2015 (Lync 2013).
Note Lync 2013 was upgraded to Skype for Business in April 2015.