So sorry you are going through this. My cording went away last year after PT manipulation and home stretching exercise, however, it's B-A-C-K! Now instead of 1 cord, I have 2. Lucky me. Kind of feels like our arms are being ripped out of the skin, right? Due to the shelter-at-home, my PT was cancelled but I was able to get a video appointment. She's shown me an additional stretch which, while excruciating, I think it's helping a little. It's been explained to me that it like a blood vessel vein, but it's a lymph vein that's basically backed up with lymph "sludge." I've been looking on YouTube for an example – not sure if you're doing this one but about 2:20 it shows the PT stretching from the pectoralis muscle next to the breast tissue. This is now starting to help me somewhat. It's also important to do your lymphedema exercises 3X a day. I hope you get relief soon. This stuff is painful and annoying.