Serious question out of sheer curiosity, but can't resist to add this silly comment below..

Asking for a friend.

Asking the real questions here. I, too, would like to know this

HH Holmes though I think he only used them once the victim was dead

You know about hidden gun furniture right? If not know now that guns were hidden even inside tables. So, what do you think?

To be fair, hiding a gun in a piece of furniture is orders of magnitude easier than a trapdoor setup.

Can't prove a negative, but a cost benefit analysis says it's set unlikely. Think of what you need:

• big enough so your victim can't hold onto the edge
• well engineered mechanism - quick, but also able to carry a (potentially fat) person
• well hidden, e.g. fine working of the edges. Or a carpet over it, but that's additional work to make sure it doesn't get stuck anywhere. And then carpets are your "ammo", and the type of people to have this probably aren't gonna have a cheapass ikea rug in their personal office.
• the whole structure of the building, below that office, needs to accommodate that functionality.
• And what even happens at the end? Is it so deep they die from fall damage? That means it needs to be tall enough. Are there spikes at the bottom? That's a mess to clean up.
• And forget about non-lethal because then word is gonna get out and it's just gonna become real awkward.
• Speaking of cleaning up, one way or the other there's a body in your house now. If you need henchmen to clean that up anyway, they could just do the killing directly.

Those are all not unsolvable issues, but they all make it more expensive. And what's the benefit that justifies that cost?

You'd get bored of the novelty long before you kill the amount of people that justifies the expense.

Answering my own question, I forgot about Jeffrey Epstein.
He is rumored to have had on on his island.

I now remember that Jeffrey Epstein is to be rumored to have had one on his island.
A trap door leading directly to the sea.
But it's unclear what it's purpose was.

Aww, shucks, then Thats no fun