Use the Saute function to cook off the liquid in the Instant Pot without the lid. The simmering liquid will evaporate and thicken in the process. Make sure to stir frequently to prevent burning on the bottom and to mix the contents for even evaporation. Note that the flavor and seasoning (such as salt and sugar) will become more concentrated as a result. 

Make a flour or cornstarch slurry. Mix 1-2 tablespoons of all-purpose flour, corn starch, or arrowroot flour with 3-4 tablespoons of water or the liquid from the pot. Once smooth and thick, stir it into the hot soup or stew to thicken it. 

Add heavy cream and grated cheese to thicken and add luxurious rich flavor.