What is the best way to achieve what I need here, which is a breve that covers the whole of the open metre passage, ideally with playback to match?
I could hide the rests, of course, but that stops playback at the end of the breve in any case. It just so happens that the duration of the free metre passage corresponds to a double-dotted breve:
But that doesn’t look right in context. I’ll go with option 1 unless there’s a better way.