Narrowing and widening w/o quiting interleave mode

I'm copying my original question from #43

Is there a way to control narrowing so it's narrowed by default, but I can still pick at the outline when I need to, w/o quiting interleave-mode?

I've realized I can use widen in interleave buffers. So if interleave-disable-narrowing is not enabld globaly, moving about (Alt-n, Alt-p) will re-narrow the buffer. In this case, it'd be nice to be able to narrow back to the original segment (i.e. toggle narrow/wide).

Maybe a narrow command that records the segment which was active when the buffer was widened.

Hope it makes sense.