The reason you harden them off is to get them used to the UV light in natural sunlight. Under lights they are not exposed to it and will burn or wilt if put in direct sunlight all day. That is the only reason to harden them off but they still need light after they come back inside. They need the same amount of light as they had before. Just subtract the time outside. Gradually increase the time outside and decrease the time under the lights. Once they are outside all day you no longer need the lights

You don't need indoor light. Leave them outdoors. Move them in and out of shade till they can stay out without sunscald. Bring them in only for really windy, rainy, cold weather. Otherwise natural light times are ok from the start of hardening.

You don't need indoor light. Leave them outdoors. Move them in and out of shade till they can stay out without sunscald. Bring them in only for really windy, rainy, cold weather. Otherwise natural light times are ok from the start of hardening.