Usage
Click the stretch toggle button to activate it.
While the toggle button is active, you can click near the start or end of any track in the track selection box to activate it. Then while holding down the middle mouse button, you can drag the start or end to another frame location.
Comments
If the start and end sides of a box are very close together it may be difficult to select the proper side. This can be solved by entering a smaller range of frames displayed in the from frame and to frame data input boxes at the right of the track selection box.
Although tracks apply only to transformations, existing sequences for scaling and orientation will be stretched as well.