I’ve always used Toolbar Pushback. In fact I’ve never not used it so I don’t know how the sim behaves without it. It has an option to stop the jetway disconnecting.
When the jetway connects, the door opens automatically, but you can open it manually too.
If you shut everything down, the ADRIUs will beep.
There’s lots of videos out there regarding the A320 operations. Search for Turkish Airlines… and whatever topic you are interested in, as they’ve published recordings of their sim sessions.
In short, to shut down:
Park Brake Set (& pressure checked)
APU Master On
Once the APU has started, APU Bleed on (if desired)
Engine Master switches OFF
Once the engines have stopped:
Beacon OFF
Seatbelt signs OFF
Screens OFF
Cockpit lights, DIM all (except for dome if it is dark)
To completely shut down the aircraft:
Crew Oxygen OFF
ADIRUs OFF (3 rotary dials, top left)
APU OFF
wait until it has shut down THEN wait a further 2 minutes to ensure the APU door has fully closed, otherwise next start you’ll have fumes in the cabin
After 2 minutes, both batteries OFF
Hopefully we’ll get a ‘turnaround’ state so that when we enter the cockpit, all relevant systems are already running and all we need is plug in the flightplan and call the tug.
I never experienced any issue with jetway disconnect itself in the default stock system via the Ground Services ATC menu. I know the Stairs disconnect itself, but never jetway.
That being said, Jetways do disconnect itself if you request pushback while still having the jetways connected. Or maybe if you disengage parking brake and the aircraft “moves” a little, then it could think that the aircraft is start moving so it can also disconnect. Or it could be based on your engine state, if it’s starting it can disconnect too. (But this is just my theory, I never really done this)