This is not "official", but I can tell you what I found when I removed one. The vents have two plastic tabs at each end that hold it in place. In the vent that I removed, the tabs at the lower end were much shorter. Just using my hands (no tools!) I carefully flexed the vent by pulling up on the center while pushing the lower end toward the center to increase the flex until the lower end tabs cleared the metal edge. Gently pull the lower end out just enough to clear the edge, then release it and slide the vent back down to allow the upper end tabs to clear the metal edge. These upper tabs are about 1/2" long on my vent. Good luck.
