Hi
"Is it possible to add a music track under video clips without switching to the timeline display? Thanks!"
In short...No.
Although you can add sound files to the storyboard mode, they behave as image files in this display mode and are inserted between the clips.
Back in timeline mode they will be on the soundrack line but inserted between clips as expected. If you want to add a sound clip you must use the timeline mode.The sound block can be moved along the track to position it under a particular video clip and the sound for that clip can be muted.
Nat