I think it is not possible to unlock a screen altogether.
Basically, see here:
Studio Community Edition runs with a User Mode Robot Service. It means that if you log all the users out, it will disconnect the Robot service and no scheduling will be possible via Orchestrator.
However, if you are already logged in, Orchestrator will take over that session. This is what happens when you run a process from Orchestrator on an active user session. It basically runs it right away.
I did not test it, but it will most likely also take over the session if you have your screen locked (not slept). This scenario is not supported with the User Mode Robot and thus should not be counted on.
There will also not be a way to unlock the screen.
The machine-wide robot service (available via MSI installer) will also not allow you to unlock the screen, because Orchestrator will create an RDP session to the machine. Such session also cannot be unlocked.
I hope it answers your question