I think what op is trying to ask or is looking for is an alternative from molinaseca that does not go via ponferrada and avoids lots of road walking of the cf. it is possible to reach olvidado from the bridge on LE-142 crossing river boeza, going perhaps via san tomas de las ollas. this would definitely need a research in advance.
what google offers, but some road walking can be cut by researching paths.
from my memory of writing the guide the last day on the olvidado (congosto - cacabelos) is practicaly
all on asphalt, so I'm not sure if this is a viable alternative if the op is looking to minimize the asphalt.
it would be a challenge to find a less asphalty route from molinaseca to cacabelos. ponferrada is a tough cookie, industrial zones are popping out all around it. so far, the only viable alternative that I can think of is from camponaraya to cacabelos via carracedo, and there is still the road from carracedo to cacabelos. I've researched carracedo - villafranca del bierzo via valtuille de abajo, but it's not been tested yet. if you are interested?