There's not until/unless dwarven civs can have cultural differences. The vanilla mountain culture might not do it, but the Banners of Jumping might, due to being escaped slaves from the goblin civ.
In which case the UI and other code needed for a playable civ to have slaves would have to be written (and tested).
Presumably goblins have
always stolen children to sell them as slaves, even back in the pre-3d era, but we never saw the slaves. It's a relatively small matter to have the slaves show up again (for example, they could sell them back to you, or goblin armies could use them as laborers). It's much harder to expose the goblins' side of that process to the player. For one, you now have people in your community who don't want to do their assigned work, so you have to motivate or threaten them, which has never even been part of the model before. They may also try to escape, and for that not to be trivially defeated by forbidding the door, we need more advanced pathfinding that can decide to go through forbidden doors. Slaves aren't allowed to eat and sleep whenever they feel like it, so we need controls to set up schedules for that stuff. And so on.
Or you can declare that (1) dwarves are the playable civ*, and (2) dwarves don't keep slaves, so implementing slavery as a player-civ feature would be pointless, and thus save a whole lot of effort.
* For fortress mode, I mean. Adventurer mode doesn't have the same demands.