I might not understand your question, but let me take a stab at it. If you are in flight and you have turned on the autopilot with the fuse panel switch, activated the autopilot with a flight plan active, the autopilot is controlling the trim. If you have, only turned on the power to the auto pilot on the fuse panel switch, the trim button on the fuse panel should control the trim.Have a question regarding trim servo operation (G3X System). When auto-pilot switch is turned on....do you loose Control of trim via panel switch? I do on mine.
You cannot just connect both trim controls at the same time - if the EFIS commanded up and you manually commanded down, there'd be a direct short. If you want both, connect both outputs via a 'relay deck' which prevents shorts. Ray Allen sells them, or build your own.