Audacity 1.3: Collapse/Expand Tracks
In Audacity 1.3, every track has an upward-pointing triangle at the bottom of the label area on the left side of the track. Click it once to collapse the track to a very small size, and click it again to expand it back to its previous size. Note that as in previous versions, you can resize a track by clicking anywhere along the bottom edge and dragging up or down.
Before clicking on the collapse button for the top track
After clicking on the collapse button
After selecting 'Collapse All Tracks' from the View menu