Setting path length for diagonal paths?

Say I want to embolden something manually. With horizontal and vertical stems, I can use the info widget thing to just set a new length for a path. This is not really possible with diagonal stems (e.g. the asterisk). How would I do that?

  1. Constrain H-V with lock symbol
  2. use up/down arrows in width or height value fields
  3. You can see segment length with one of the plugins from the plugin manager

Okay, and how do I e.g. thin slashlongcomb while keeping the slant?

You can drag two end points freehandedly, and the nodes should snap into the diagonal angle.