I have been using Inkscape for some months now to edit and maintain a transit map of San Francisco. For the most part I am very comfortable editing paths, removing and adding nodes, snapping to grids and objects and the like . . .
But what I have yet to figure out, is how to bring multiple lines together, in parallel, either stuck together along their edges or separated at a constant distance, like railroad tracks.
One technique would seem to be to create a wider path objects beneath a narrower path object, then snap their nodes together, to create a path with an outline, but I would really like to combine two or more lines in parallel, as you often see on transit maps. If anyone can shed some light on my desire, I owe them a cookie!