No idea if this is right, but I’ve started reading stuff like that as a pause, like a comma. I’ve never seen the tilde in Japanese, but I have seen consecutive numbers to mean a range, and that’s what I do with those.
I’m assuming it’s not pronounced にょろ when you say it out loud / in your head.
I remember having the same question a while back, I believe it’s から. I was reading something that also had audio so that confirmed it. Grain of salt though because I don’t remember what it was so I can’t prove it
X~Y was actually the first thing I ever looked up in a Japanese grammar dictionary because I had this question too and couldn’t figure out how to google it back then . But I wiki’d it because I realised there might be a different answer.