Thanks, Redwitch. This is actually the one I tried when I mentioned above the one described on Knit and Tonic. There must be some particular step I do wrong, though.
Oh, I just see your edit. My eye glanced over it thinking it was your signature. 
Yes, I was always able to cut the yarn and unpick it, but thought it would be much cooler and faster if it unzipped. Especially when I have to do over 100 provisionally cast on stitches.
I had not tried the video on this site because I generally do my knitting at home, especially something that requires concentration and learning, and I have dial up at home so can’t watch the videos.
But the link Ingrid provided actually worked pretty well for me. I am going to use that one. Thanks, everyone.