Clips cannot be extended from the start

[Elliott Sales de Andrade]

Using the resize tool, you can extend a clip from the end (i.e., towards the right, from the right end). You can also shrink it from either end (i.e., from the left end towards the right, or from the right end towards the left). However, you cannot extend the clip from the start (i.e., to the left, from the left end).

Since images have no inherent length, there's no reason this should be limited. For audio/video, this should basically be the same as moving and extending the right end (up till the original length).