Length changes of the (predefined) hook aren’t applied to the line for some reason. They remain the same length as before. If I create a copy of the hook, change its length and assign it to the line, it works.
That’s strange. I just tested it too and it definitely doesn’t work. Is this a Mac vs. Windows issue? The hook changes don’t show in the preview area of the line editing dialog either.
Rule 1 on editing lines annotations is always work on a duplicate of the annotation or all your existing lines that use that annotation will be affected! (Same applies to line bodies)