is different tire pressure on 3 of the tires harmful
Well it all depends how how much difference there is. Why not just set them all at the pressure listed on the door drivers plaque or in your owners manual ? If you are asking about tire pressure that makes me think you don’t rotate your tires as you should.
All four tires should be at 35psi cold. If there’s a significant difference your tires will wear unevenly.
I have seen some customers with OCD complain if the tire pressure display shows 34, 35 and 36 PSI. 34.5 is close enough, it is not that important.
… and the vehicle’s handling could be compromised.
Do you have the ability to inflate the tires properly yourself?
If not, I suggest having someone do it for you.
What are the actual pressures? Are any of the tires in the sun when you measure them?