Nikon D6 Reference Manual page 640

D
Deselecting Pictures
•
To deselect a picture, hold the J button and press the center of the
multi selector again.
•
Transfer marking can also be removed using [Select to send (wired
LAN/WT)] in the playback i menu.
•
To remove transfer marking from all pictures, use [Wired LAN/WT] >
[Options] > [Deselect all?] in the setup menu.
A Using the i Menu
You can also mark the current picture for upload by choosing [Select to
send (wired LAN/WT)] in the playback i menu.
588
Upload to Computers and FTP Servers