You had to alter your firmware to do that, just as I had to alter my 1300LM's firmware to get lane assist, junction view, and the speed limit indicator. The OP didn't specify, but based on his questions so far, I don't think he has changed his firmware from what Garmin provides. Thus the answer I gave.
If he wants to change the firmware to add the hidden tracklog support, we all know now that it is possible. But what are the chances of bricking the device? :)