Right now you can place unconscious captives into either the sacrifice table, a wheel of pain, or the (battle pass) gibbet. The sacrifice table will allow you to hold the captive there indefinitely, until you wish to sacrifice them. The other two items automatically convert them into subservient thralls provided there is enough food.
But none of these items allow you to render a captive unconscious again, in order to transfer them somewhere else for a later purpose.
I would love to see a new type of item that allows you to keep un-broken prisoners indefinitely, and then (if you wish down the road) to drag them out again using your bindings, to be placed somewhere else (perhaps in a wheel of pain, or onto the sacrifice table, or back into a different holding cell).
Shackles that could be placed on the wall of a dungeon, or an actual prison cell that might look like a regular iron-grate door, or a courtyard stock, or even a functional cage similar to one of the existing decorative cages – could all serve this basic purpose, and allow a Clan to keep a reserve of hostile (unbroken) captives for any purpose. It would make a great addition to the world of Hyboria, and would look pretty cool if you built an entire dungeon filled with shackled prisoners. Need three more sacrificial blood flasks to power up your teleport pad? Just head on down to the dungeon and pick out some unfortunate prisoners!