Could you please provide an example to draw a geoline based on a OSM way? All of your examples seem to refer to relation objects in OSM, not to ways. I wasn't able to modify the geoline example "Interstate Highway I-696" to work with an OSM way. If this is a technical restriction, it should be mentioned in the docs. Thanks a lot!
Topic on Help talk:Extension:Kartographer
Probably a too late answer, but OSM cannot identify entities other than relations, in a stable way. Anyone is free to move/replace/split/combine ways "as they like". OTOH, editors usually keep relations in place...