Like 'resize', but for lengths

Suppose I'm drawing a rectangle on screen. I can resize it — change its length and/or width to make it bigger or smaller overall. Now suppose I'm drawing a line, which I can make shorter or longer. Is there a word describing this action, other than resizing the line? It's one-dimensional and doesn't really have a size, and there's no such word as relengthing.

The verb you want is resize.

You can resize many things:

• images
• Vectors in C++
• DOM elements, using CSS
• ext4 filesystems
• A window

And many others.

Some of these things are inherently two-dimensional, some are not. All of these things are virtual, computer-based things. You typically do not resize physical things, but in a computerized environment anything can be resized.