HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Terminal Server\CentralPublishedResources\PublishedFarms\<collection>\RemoteDesktops\<collection>

ShowInPortal     REG_DWORD     0x00000001 (1 means SHOW the desktop connection icon, 0 will hide it)

http://www.systemcentercentral.com/ws2012-vdi-tip-how-to-publish-a-full-desktop-alongside-published-apps/