Thanks thcilnnahoj, yes it all helps – the phantom advice is excellent, but I cannot get that far:
I have the setup as you described – the arranger shows one bar only. I Locate the bottom handle, at the bottom right of the track in the arranger, and get the double-arrow, for dragging.
BUT when I click + drag, no dragging happens.
I messed around with CTRL+click_drag, and a black area is shown as I drag, which vanishes when I let go. Do I have to ‘unlock’ the track in some way?