The Timeline in 3DTitles displays additional information about the subtitles in somehow less compulsive than the Subtitle Depth Graph way.
The blue line indicates the picture's depth according to the subtitle's current horizontal and vertical position. The green line, on the other hand, indicates the subtitle's currently depth. The orange vertical lines indicate the shot changes in the video. The red vertical line shows the current video position. A sequence of vertically positioned triangles may be present to the left and right of the subtitle. They indicate that either the subtitle's In-Cue or Out-Cue are snapped to a shotchange.
But the Timeline doesn't do only that - it also provides multiple options to adjust the time code of the subtitles. You can drag the whole subtitle to a new position using the mouse, or if you want to change in- or out-cues only you can drag just the left or the right bound of the subtitle. By pressing the Alt button, while modifying a cue point, you can also move the previous or next subtitle's In/Out point as well.
Note: The timing of the a subtitle can also be modified by using the built in In Cue +/- 1 frame (Ctrl +- and Ctrl + = ) and Out Cue +/- 1 frame (Ctrl + [ and Ctrl + ]) commands.
In addition, by pressing the triangular look button 
on the top left part of the Timeline you can change the zoom level of the Timeline.