On the Lync 2013 & Skype for Business 2015 PC client it was possible to use the shortcut key of Ctrl + Shift +T to blind transfer a call from a conversation with minimal clicks. In short, from the conversation window you could press Ctrl + Shift +T, type the extension number and press ENTER and the call was transferred.
One unique thing about using the Ctrl + Shift +T shortcut is that it opened a Lync 2013 window that was different than the window that was opened if you clicked Call Controls | Transfer on a conversation window. (below is the Ctrl + Shift + T window and the standard Skype for Business 2015/2016 transfer contact search window)
Now in the Skype for Business 2016 client the “Ctrl + Shift +T” shortcut appears to no longer be available. (Note: The Office documentation says that Ctrl + Shift + T is “Not available with all Office 365 subscriptions.” but in our testing it does not work even with Skype for Business Server either.)
So its back to Call Controls | Transfer
then type extension number or contact name and click “Transfer Now”.
If you need to transfer a lot of calls efficiently you may be a candidate for an attendant console.