Add pasta and broth to the Instant Pot and stir to combine. Ensure all pasta is submerged, then secure the pressure cooking lid.
Using the display panel select the PRESSURE COOK function and adjust the time to 5 minutes. (If you use another pasta, set the time for 1/2 the stovetop cooking time, rounding up if needed.)
Meanwhile, in a large bowl, toss the broccoli, walnuts, oil and garlic. Set aside.
When the cooking time is up, carefully quick-release the pressure. (As with any starch dishes, be aware that liquid may come out of the vent on release. If that happens, close the vent, wait 30 seconds and try again. Repeat as necessary.)
Move pot contents to a large covered dish, then rinse the pot and return it to the cooker base.
Place the broccoli and walnut mixture in the Air Fryer Basket. Place the Air Fryer Basket on its base, lower into the pot and secure the Air Fryer Lid.
Using the display panel select the AIR FRY program. Adjust the temperature to 360°F and the time to 9 minutes, then select START.
When the display indicates “Turn Food” remove the lid and place it on the protective pad. Use tongs to toss the broccoli and walnut mixture, then replace the Air Fryer Lid to resume the program.
When the program is complete, place the lid on the protective pad. Toss the broccoli and walnuts with the pasta. Season to taste, top with parmesan and serve immediately.