Regrettably, synchronization isn’t possible using the new app as they do not allow you to automate the unlocking of a door. This is a change in design philosophy from the classic app.
I think the best way around this would be to use an electric strike in place of the current door knob. That would give you two locks on the door: the deadbolt and the electric strike.
(An electric strike is fairly common in commercial buildings, not homes. If you think of the systems where Someone buzzes you in at an office or apartment building, that’s typically an electric strike. The person does something to release the strike, you typically hear a click, and then you can pull the door open. The device holding the lock in place is the electric strike.)
See the following thread for discussion of using an electric strike with smartthings. However, you don’t want the strike to look like a door lock to SmartThings or you’ll run into the same automation problem. Instead, just make it look like an on/off switch.
And another discussion thread on a similar project:
