On the bottom left of the timeline, click Track+, or from the Timeline Gear menu, select New Video Track.
Depending on your selection in the Add Track box in Preferences Timeline Editing, a new track is either added to the version on top of the last existing track, or to the track above the focus point.
If you want the track to be added below the last existing track, press Ctrl while clicking Track+. You can re-order your tracks, or even move a track to a different version by dragging the track from the handle at the left of the track.