the I see where you're coming from now. There has been the suggestion that it would be handy to have the audio blue-line adjustable on the timeline as well as in the preview window.
But in lieu of that enhancement, consider playing the timeline until it reaches the IN point where audio is to be adjusted. SPLIT the track at that point. Play to the OUT point and split again. Then click the newly split-out clip's audio track and you will see it isolated (in white) in the preview window, showing the precise IN/OUT points. Perhaps this approach will suffice for the time being.
If you want to be selective, click the small chevron to the right of the split button to choose which tracks to split.