I do remember seeing a close-up photo of that whole panel (can't remember if it was a real set photo, or one of Donny's amazingly photo-realistic recreations), that had two small rounded inset cubicles with a surfacing that conveyed a visual queue strongly resembling a miniaturized transporter chamber. I also remember seeing early Phase II bridge diagrams that had a full-person-sized intra-ship transporter in that location (and, yes, the Mego toy as well), but that definitely changed somewhere along the way, and by the time TMP rolled out, it had split into two smaller ones, that could only be used for replication - I think more for tools, maintenance equipment and such than food. They were difficult to see, as they seemed to be covered up by two pieces of heavily tinted glass...er...transparent aluminum.