On Audis with the same system, the nozzle is "extended" by pressure, which means there are no mechnical locks in place.
The way we would work, say prep the car for paint, is to gently pull the nozzle out, you can do it manually, until is sufficiently out to grab it and, usually the cover is clipped in place. Once the cover 'clicks' in place, slowly lower the nozzle to its rest position. The key is to do all movements gradually, if you rush you can break the clip on the cover or worse, as one of the fellas in the workshop did, broke the bracket holding the nozzle .... bumper down and finding a replacement was a pain.
I recently took off my wife's Lexus bumper for paint and the procedure was the same, with the different it had a metal slider clip - clever.
EDIT: I forgot, I;ve neever tried on the Superb, I have to go to the garage now and will attempt and re-post tonight, but on the other cars it was enough just to patiently use fingers/nails to "catch" the edge of the cover, and then start the pull ... lighty so.
If you have weak fingers or bite your nails, or the cover is very flush, a trim removal tool - plastic one, of course - can do the trick!