Don’t take it all down. Start at one end, remove a few grommets worth of cord, and replace as you go.
Or, zip tie it in enough strategic places, if you think that you can remember the cord pattern. Take pictures first.
Find a crochet needle that the cord will fit inside of, use it as a fid. Start with about 6 inches long, crimp the cord inside at the very end, and just cut off a quarter inch if you need to start over.