When using the TEXT editor (not the subtitler), each entry is a clip that appears above the video track. Those text clips can be moved individually or in tandem.
Subtitling would normally be composed after editing is complete.
There's an auto-generating feature that's worth trying. Click the Audio tab in the menu bar, then click Speech-to-Text in the toolbar. That will produce an overlay track with individual clips.
If instead the Auto Subtitle toolbar button is used in the Subtitle editor window, it will produce a typical list but no overlay track. Corrections can be made by selecting each entry for editing.
