Soak the lentils in water to cover for 8 hours or overnight. Drain the lentils.
Place the soaked and drained lentils, onion, bell peppers, carrots, garlic, couscous, vegetable broth, salt, pepper to taste, bay leaves, and thyme sprigs in the Instant Pot and stir well to combine.
Secure the lid and set the Pressure Release to Sealing. Select the Pressure Cook setting at high pressure and set the cook time to 3 minutes.
Once the 3-minute timer has completed and beeps, allow an natural pressure release for 10 minutes and then switch the Pressure Release knob from Sealing to Venting to release any remaining steam.
Open the pot and discard the bay leaves and thyme sprigs.
Transfer the couscous-lentil mixture to a large bowl and allow to come to room temperature.
To the couscous-lentil mixture, add the extra-virgin olive oil, vinegar, dill, parsley, olives, tomatoes, and salt and pepper to taste. Stir to combine and taste for seasonings, adding more salt and pepper as needed, or a splash more vinegar for acidity.