How do customizers make chain link that is flexible and posable? thanks in advance

Ive used one way, having a chain necklace and taking one of the very thin plastic covered wire ties that comes around figures in package and stripping it down to just the bendable metal wire part and putting it through each link on the chain

That's the only method I've heard.

I guess you could try to find a soft rubber chain accessory from a toy and threading a wire into it in a similar fashion, but I honestly think that would be harder and not really work or look any better.