I don't see a way to enable waveforms, and that's probably due to the limited screen space available for tracks. The best way to have waveforms show up is your "dupe" approach, and you can mute the main clip (or delete the audio clip) once you've got everything synced.
If you'd like to let Cyberlink know that you'd like to have some way to display the audio on the main video tracks, go to
Settings |
FAQ & Send Feedback. Maybe they can add a quick way to toggle between video thumbnails and audio waveforms.