rncbc.org a.k.a. Rui Nuno Capela

There's no magic key combination, yet. There's currently two ways to time-stretch an audio clip:

1) in clip properties dialog (Edit/Clip/Edit... or double-click on the clip region) you can tweak the time-stretching coefficient of the audio material (in percentage); this goes independently of clip length which you can also tweak otherwise;

2) by SHIFT+dragging one of the audio clip edges (left or right) to a new nearby location, most often to fit the clip length into a bar multiple; the clip length will change and the audio will be time-stretched in proportion to the change in length. Dragging the edges without pressing SHIFT key will change the clip length but won't affect audio contents;

The latter might by the magic you're just asking for, so let's try it :)

Cheers