You can stretch the time of an audio clip on the Timeline by holding [Shift] then dragging the handles on the selected clip.
What is sliding stretch in audacity?
Sliding Stretch... allows you to make a continuous change to the tempo and/or pitch of a selection by choosing initial and/or final change values. Tempo changes made without selecting a pitch change preserve the original pitch, and pitch changes made without selecting a tempo change preserve the original tempo.
How do I change the Timeline in audacity?
Timeline right-click context menu
Right-click on the Timeline gives a short context menu. Enable dragging selection: When disabled (default), left-click and dragging the Loop Region adjusts the Loop Region only, leaving the current selection or editing cursor unaffected.