Start by washing and peeling the potatoes, then dice into medium sized cubes. Place a steaming basket or a trivet in the Instant Pot, add about 1 cup of water to the bottom of the pot.
Add the potatoes, and put the eggs on top. Cover with the lid, place the valve to sealing position. Cook on pressure cook/manual - high pressure - 3 minutes. When the cooking ends, do a quick release and open the lid. Quickly put the eggs in an ice bath to stop the cooking process (you don't want overcooked eggs).
Take the potatoes out, drizzle with a little bit of white vinegar and let them cool down for at least 10 minutes (preferably more). Chop the eggs, then add them to the potatoes along with the celery and green onions. You can reserve one egg to slice later and use for decoration.
Make the dressing. Whisk the mayonnaise with yellow mustard, celery seeds, salt, and ground black pepper. Add the dressing to the potatoes, and give it a gentle stir until everything is well coated. Chill the salad in the fridge for at least one hour before serving. The longer this salad sits, the tastier it becomes. Whenever possible, I let the salad sit in my fridge overnight to enjoy the next day.