Why was I not able to actually frog back my helical Rosebud until I'd screwed up something else, too?
I caught the problem weeks ago. See, I'd forgotten to look at the pattern when it was time to start the empire waist and hence didn't know about the decreases in the first row of ribbing. As my less-used boobs deflate, I'm considering switching to a smaller chest size (I still need all the room in the hips, never fear), so I really can't afford to ignore those decreases.
I threaded a spare Addi through as a lifeline:
and left it there for a month, until my almost-done Parrot socks* got long, but not wide enough. Time to rip back to just after the minimal calf shaping I put in, so that I can add some more. Threaded an Addi 0 as a lifeline, unraveled away, and remembered: hey, there's that sweater, too, with the four live strands and the elastic thread skipping promiscuously from one to the next.
Somehow the act of frogging the sock freed me to calmly approach the sweater. I spread out the four balls of yarn on the floor in a circle around the sweater, grabbed the card of elastic thread, and carefully wound one, wound the next, detangling the elastic as I went. It took less than 15 minutes in the end.
* The only picture I have for those right now is of the ball of yarn, pre-socks:
That ball! It took me a week of stolen moments to wind. But I've worked over three-quarters of the yarn, making one sock from each end, and it's stayed usable the whole way down.