Ok, so I finally got around to repotting the poor Philodendron. But it looks much better now. When I removed it from the other pot, I couldn’t believe it, but there were no roots going into the soil. I don’t know how it was surviving. There were three or four very green and healthy looking stems tangled up with the pile of dead vine. I found a few places where it looked like there were maybe root nubs that should quickly grow into viable real roots. I cut the stems into six pieces that had a plantable root nub, and stuck the ends with the nubs into the moist soil. It should be fine. If it survived that other mess, I don’t think transplanting it into potting mix will hurt it.