As I often use a radio mic on one channel and on camera effects mic on the other, it would be useful if I could individually review each channel in the trimmer.
I'm fairly certain that this can't be done though would like to be proved wrong, please :-)
But, if you don't want to getting too busy with the timeline, sometimes it IS a bit of a pain AND if you do a fair bit of audio work anyway, you could, if you had/have Sound Forge always open a copy in Sound Forge FROM the trimmer [EDIT} by right clicking on the Trimmer Event and selecting Sound Forge[/EDIT]. You can then highlight the areas under question and play-back/audition just them.
You might even find other audio management tools within SF that you may wish to do prior to getting to the Vegas timeline.