I recently took a flight from Dublin (DUB) to the US, and so I went through US immigration and customs preclearance in Dublin. I have Global Entry and used the automated kiosk. I realized afterwards that I hadn't ever been asked whether I had any goods to declare for customs, and it wasn't clear how I should have declared them (if I had had any).
After entering the preclearance area and having my bags X-rayed, there was a lane for Global Entry with the kiosks. In the past, when I've used a Global Entry kiosk in other places, it has asked me to select answers to the usual "landing card" questions: any goods to declare, carrying any food, etc. In this case, the kiosk just took my photo and printed a receipt. It didn't ask me any questions, and I didn't see any place where I could have selected "goods to declare". I think it was just "touch screen to begin", "look into the camera", "take receipt to the desk".
Next, there was a desk with a border officer. I gave him the receipt from the kiosk, and he looked at it and sent me through without asking any questions.
I assumed at this point that there would be another desk where I would be asked customs questions, but in fact after walking away from the first desk, I realized I was already in the gate area, and there were no further checks.
I also didn't notice having gone through a "nothing to declare" channel at any point.
So, if I actually had had goods to declare, what would I have needed to do? Was there a button on the kiosk that I overlooked? Was I supposed to proactively announce it to the officer at the desk (I didn't see any signs saying to do so)? Should I have stood in the regular queue instead of using a kiosk?