Like in the trailer. How do you do a silent kill with a dagger by slitting someone's throat on PC?

it's a finisher. If your backstab does enough damage it triggers the animation.

To get a almost always backstab, the assassins blade perk in the sneak tree increases sneak damage with daggers by 15x.

I'm wondering whether you can use both daggers while dual wielding while sneaking or if it only let's you do the attack with one. Does anyone have the answer to this? Because, I've heard you can't do power attacks while sneaking, so that would stop you from being able to attack with both at the same time technically, right?