Comment 8 for bug 171479

Oh, there is a much easier way to achive both trim and extend.

• Just select path A (which should be trimmed or extended/prolonged), then press Ctrl and drag at the diagonal arrow in the direction you want.
• If you have enabled snap to path and snap to cusp node, you can shorten (trim) path A if it was to long (intersecting path B). And you can extend (prolong) path A if it was to short.

For a sketch and more details see the answer from Roger Attrill at stackexchange: http://graphicdesign.stackexchange.com/questions/21750/how-to-prolong-a-straight-line-or-path-in-inkscape/21758?noredirect=1#21758

This bug should be closed, as this workflow is really intuitive.