PathTruder utility allows to create a surface by extrusion of a shape along a path. The path is defined as two sets of lines, provided to PathTruder as two LDraw files. The shape, also a set of lines, is the third required input file. The fist segment in shape file (in red in the image above) defines how the shape file is attached to the path, one extremity is applied onto the first line, the other onto the second line.
PathTruder can be considered as a variant of Coverer, not restricted to straight Junction of sheet. Though it has many more possibilities, it also has some restrictions - for example Coverer allows the two path lines to have a different number of segments. Another difference is that PathTruder doesn't cerate conditional lines. You'll have to use Edger2 for that.
It is a simple console application, source code is provided below to anyone willing to integrate it in a more palatable user interface. You may also use Michael Heidemann LETGUI front-end (highly recommended!).
