How to: show only one channel (of stereo) in frequency plot

Is there are a way to show only one channel (of stereo) in frequency plot?  I want this as a way to expand the Hz-plot image (of just one channel) over twice the vertical span on my monitor, in order to double the visual resolution.  That would reduce the amount of zooming I have to do, when brush-healing out coughs from orchestral performances.

Just to explain: you can completely remove a cough without destroying the primary audio this way.  It's slow, but very effective!  You have to zoom in on the frequency span, so that you can see the notes and their harmonics (as horizontal lines), and then only brush-heal the spaces between these.  It's best done no lower than about 1-2 K Hz.  And above about 4-6 K Hz, you can just brush-heal the whole region, since scant harmonics show up this high, or matter even if present (unless you're a dog, or a very young kid, I guess).

I've looked through the menus, preferences, and context-sensitive pop-up menus, and found nothing that allows this.  Forum seems mute on the topic too, so far.

If anyone knows this is not an option, please let me know, so I can post as a feature request.

Thanks very much!