It looks like there might
be an already open door there, running vertically near the right of that pic. However, there's no doubt that that corridor area outside is completely dissimilar to the one that Kirk wanders out into later, carrying his fainting bride.
Also, he seems to be carrying Odana to his quarters
. Via another door (it's the briefing room set door, but that reality-info is irrelevant here). So, was the viewing corridor accessed through there, or was it on another deck and Kirk used a turbolift to transport her to his boudoir?
FWIW, I pop for the observation room being on the upper hull of the saucer. The angles are not too far off, and the exterior hatch means that the window could literally be located anywhere
. It's alsoonly a short walk to his cabin.