@newcat sometimes you have to consider the order of your ingredients. I made a chicken casserole tonight. I quartered an onion and put that in the bottom. Two peppers, deseeded. Several carrots, topped, tailed and halved. Then chicken drumsticks. About 10 large salad potatoes, whole.
Then I poured in chicken stock (just under half a pint) and once all of that was in, I poured a tin of tomatoes on top.
It's really important that you don't mix tomatoes or any sugar-containing ingredients through your other ingredients. It will just catch on the bottom and overheat. You don't need to stir with the instant pot - the flavours will mingle just fine even though they're layered.
I use a potato starch based thickener, but the principle goes for any thickening agent - hit 'saute' and add your thickener, stirring.
Generally, also, you can adjust the water content according to what you are cooking. If the food has lots of water (veg, etc.) You can get away with ½ a cup of water or even less, because more water will be released from the food as it cooks.