In this screen capture from Star Trek VI, we see this... thing... on the floor between the helm console and the captain's chair. The "spine" of the helm console slopes downward and has the "astrogator" display, and then this structure rises up from behind the astrogator display. What is that thing?
Well, it looks to be too far away to serve as the Captain's foot rest. (Unless the Captain would pass for an NBA player, that is.) That is odd. Could it be some kind of extension of the helm/nav console, offering additional controls? Beats me.
I thought maybe they stuffed Kollos in there, to take over the navigation station whenever Chekov takes a vodka break.
It's just an empty prop that Shatner can put his foot up on when he stands to say "fire" and blows up the Klingon ship... ya know, to look all cool and dramatic and shit. The Shat probably asked for something like that from the prop department after practicing at home in front of the mirror. And that is literally it's only function, fictional or otherwise. Sulu has something similar on the Excelsior to put his vibrating tea cup on, but his retracts into the floor, cuz Sulu's all classy like that. It's the same reason they put a convenient little handle on Chekov's space suit in TWOK, just so Montalban can grab it and lift him off the ground all bad ass, no handles on those same suits in TMP you'll notice. It's all prop wank, sci-fi productions are full of 'em.
Kinda looks like the controls to the ship's music system But I suppose it'd be more controls and status displays for just the captain. Use to be the ship's chronometer was there but it got moved to the main viewer though.
It covers a part for the gimbal/gimbel?, which they mounted the set on for the vibration and to create a more dramatic/realistic effect during the battle scenes.
If the coffee table really retracts, that means there's a hole in the floor of the set at that location. Meaning that when the set is changed from Excelsior bridge to Enterprise bridge, they have to cover that hole somehow... And a simple piece of carpeting won't suffice, because the seams would be way too obvious and reveal the swapping trick. So, the extension to the Enterprise helm console gets its explanation right there and then - fancy manhole cover! I don't see any evidence of the coffee table retracting, though. It's there even when Sulu goes to battle. Timo Saloniemi
Don't be such a square, not only does the table retract, but the workstations in the rear of the bridge revolve around to reveal a full wet bar. The Hi-Fi sound system is the shit too... and guess where the disco ball lowers from.
I will add the totally off-topic comment that that helm/nav console rocketh mightily. Some pre-LCARS graphics, plenty of physical knobs and buttons, and that way cool silver steering wheel/joystick thingy.
I'll say an early hologram transmitter, so as to have an image angled such that only the captain can see it. It appears as an in-air HUD, floating before the screen, but not distracting the helmsmen. That or non-essential displays for the helm officers that they have to turn around to use.
I've always been a big fan of the STVI bridge. It is both aesthetically pleasing and functional looking.