The answer is:

In P3D and with the CS B767 loaded at an airport gate, go to menu Add-ons, GSX, Customize Aircraft...

The GSX - Customize Aircraft windows opens. On the left side of the aircraft figure, click on the green rectangle to the right of "Pax1". A pop up window shows up to allow you to configure that door. You could then enter the door position to the right of the "Position (m)" label. You can enter it manually or use click on the "Customize in 3D editor" button. My numbers are from left to right: -2.41, 20.0, 4.54.

Hope this helps.

David