Maybe this will work for you...

With the song and style loaded and playing, use the 'Mixer' button to bring up the Mixer in BIAB. You can solo the Guitar track to hear its volume alone if you choose. Select the volume function and you will be able to raise or lower the volume of any track or tracks.

If there is enough headroom, simply sliding the low volume track slider to the right may work. If all the tracks are already relatively too loud so you cannot get enough added volume out of the quiet track, go down to the 'combi' button and slide it back to the left, reducing the volume of all the tracks. This will provide the headroom needed to increase the relative volume of the quiet track.

When you've got the relative volumes where you want them, slide the combi back up (to the right) to get the absolute volume where you want it.

John E.