When an auto attendant answers can I just dial any extension? Is direct dialing enabled/disabled from there? Is there way to enable that from the Terminal Attributes? It seems people can direct dial some extensions but not others.
TIA

as an example the caller dials x304 and is somehow connected to x301

In a nutshell, yes. The important question is to ask which Vertical system are you talking about? Like Chevrolet, there are plenty of different models marketed by Vertical.

Summit 800