I realize this post was made some time ago, but I am hoping you have found the fix.
On BT5r3 myself, using a HP Latptop. I have a Dell monitor attached to my 15 prong and still, regrettably, cannot figure out how to set it up to have an alternate display. It is just cloning what I have on my primary display.
I am hoping someone will either see this or post a link to send me in the right direction, as I am both new to BT and only an hour into joining this forum, so I am unable to post my own new thread.
Hopeful thanks in advance-