Turn on a multi-functional pressure cooker (such as Instant Pot®) and select Saute function. Add 1 tablespoon butter and 1 tablespoon olive oil; stir until butter melts. Add corn kernels and cook, stirring occasionally, about 2 minutes. Remove corn to a bowl and set aside.
Pour remaining 2 tablespoons of olive oil in the pot. Add red onion and cook for 1 minute. Add garlic and rice and stir until each grain of rice is coated with the oil mixture. Cook until rice is slightly toasted, about 2 minutes. Pour in white wine and simmer for about 30 seconds. Stir in chicken broth.
Turn off Saute function. Close and lock the lid. Select high pressure according to manufacturer's instructions; set timer for 6 minutes. Allow 5 to 10 minutes for pressure to build.
Release pressure carefully using the quick-release method according to manufacturer's instructions, about 5 minutes. Unlock and remove the lid. Add corn and remaining 2 tablespoons butter; stir until risotto is creamy, about 1 minute. Stir in Parmigiano-Reggiano cheese until melted and well combined. Garnish with parsley.