Hi, sorry for the delay. As you wrote, we have lots of stuff to do these days 🙂
I think I know what's causing your confusion. When you hit your pad, you are playing the trig articulation - correct?
When the trig pad selects what articulation to play (center for example), it doesn't currently play the stack - it only plays that articulation. So, as you say, if you want to use a stack when playing on the trig articulation - you could add a stack to the trig articulation.
We will look into this, since the stack should be triggered from the trig articulation - not just one articulation.