Set instant pot to sauté and add a tablespoon of the oil. When hot, add half of the beef cubes and brown all the sides.
Remove and repeat with the remaining oil and beef cubes. Add salt & pepper.
Sprinkle flour over the meat and stir until all the pieces are coated.
Add onions and cook until starting to soften. Stir in garlic, Italian seasoning and tomato sauce.
Add about a half cup of the broth and use a metal spatula to scrape all of the brown bits off the bottom of the pan. . Cook until thickened, about 1 minute. Stir in remaining broth, Worcestershire sauce, and sugar.
Lock the lid onto the instant pot and set to STEW. (Mine automatically sets to 35 minutes, but including the time needed to come to pressure, it takes about 45 minutes.)
When it beeps, use the quick release and remove the lid. Add the potatoes, carrots, and celery.
Set to manual HIGH for 10 minutes. (Takes about 23 minutes total including coming up to pressure.)
Stir in the frozen peas. You can use the saute feature if your stew cools down too much, but I don't usually need to.
Taste and add more salt and pepper if desired.