here is our experience: On Destiny
-the balcony unlocks by the room stewards "special key" - first cruise immediately done.
Second cruise "brought our own key
(needlenose pliers) and it hooks against one of the windows--50/50 chance one of cabins will have the bedroom window view blocked. The door has to lock somewhere.
needed to IMMEDIATELY upon boarding put our name on list to get balcony doors opened. After examination, couldn't for the world figure out how they unlocked, nor would hold--- a huge contraption called a "boot" like the kind they use to lock tires for illegal parking was installed by maintenance crew. And reason to get immediate request they only do so many balconies either because of labor involved or they only have so many boots. This boot locked onto railing, so one panel actually opend 45 degrees like a closet.
Not sure how your panels will unlock but:
So my suggestion--get to purser right away and request balcony opening.
We used are open balcony freely--great thing to bring--post it notes to put inside on glass door for another--like sleeping, went to lido etc.