I highly recommend watching the Torch Talk 102 video on Youtube (
https://www.youtube.com/watch?v=JGID2ExqBYw&t=1445s). Another one is by Glass Science (
https://www.youtube.com/watch?v=RbVpL0VdADI&t=339s). Most chain is being made with boro because you can set it down on your bench or on top of a heated kiln while working on it. I tried making it once with soft glass but it was not easy. When I'm done, I do put the entire chain into the kiln to anneal.