How to adapt the cooking time

You can check the boneless chicken thighs for doneness (taste and safety) by cutting into one or more as needed, until you see the pink in the center is gone.
Or use thermometer to tell you when interior of chicken thigh reached 165F or 74C.
Sorry, from experience and recipes cooking time is about the same as for bone-in thighs. But you can simmer in a wide pan to give them all more access to the heat and start checking at 15 or 18 minutes to see how they are doing.