If you put the headlight washer nozzles in the service position by using the appropriate command available from the Front Display Screen, the nozzle doors will be about 85% of the way open (they will be 'fully open' in the sense that that is as far as they ever open during normal operations).
You can then take hold of the nozzle door and move it forward about another 1 cm (3/8 of an inch) and it will mechanically 'latch' in the fully open position. It rides over a small cam when it does this.
But... if there is any degradation in the mechanism that normally drives the door to the fully closed position when the nozzle is extended, then it probably won't lock in the fully extended position.
In the photo below, the red arrow points at a U-shaped assembly that provides the spring force needed to return the door to the closed position, or, if you pull the door fully open, the force that is needed to hold it in the fully open position. Click on the image to enlarge it.
Headlight Washer Door.jpg