To reposition a track, position the cursor over a track until it
changes to this shape
then click and drag
the track up or down within the list, and release.
To change the height of a track, position the cursor over its
lower boundary until it changes to this shape
and then click and drag downwards
to change the height of the track.
To collapse the whole Timeline down to just the Time-track and
Playback toolbar, click.
To restore it, click the icon
again.