Yes, Matt's comment was what made me believe it's possible. But I can't [or couldn't; read on] figure out how to select the specific measures to apply the transformation to. I can select measures in the Chords view, but Melody > Edit Melody Track > Transpose > Transpose One Octave DOWN [or UP] transposes all measures, not just the ones I selected.

... Exploring further, I tried Transpose (rather than Transpose One Octave), and found that will let me specify measures.

Thanks again!