Whisk, then change the setting to “sauté, medium heat.”
Use a thermometer to check the heat periodically; when its reached 185°F (this will take about 15 minutes), hit “cancel” and use oven mitts to carefully remove the inner pot.
Let the milk cool for 40 minutes, then whisk in the yogurt. Return the inner pot to the Instant Pot, cover, close the pressure vent, and wrap the entire Instant Pot in a towel. Let the mixture sit for 8 hours or overnight.
Scoop the yogurt into a glass bowl, cover, and refrigerate until cold.