In some ways the fact that the dangers of smoking are such common knowledge these days can make it a powerful tool for character design, because it signified so many good things in the past, but signifies so many bad things now, so the symbolic attachments to it are very complex. What I'm getting at is that smoking for a character can mean any number of things, contrasting things simaultaniously even.
For example, say you have a character that's a real macho tough guy, and a lot of kids really look up to, and you want to signal to the audience that he's a bad role model, just have him smoke. It's something that looks cool, especially to kids, but it's something they'll want to emulate and something that he shouldn't be doing around them.
I have actually written quite a few characters who smoke in various story ideas, and I've used it to mean a few different things. For example, my character Agony from my novel smokes A LOT, and at first it's just explained as something she does to rebel against her sterile background. But the more is revealed about how that background damaged her, the more apparent it is that smoking is an anxious habit for her (which it often is in real life!) and that it, along with other traits like over frequent swearing, are compulsive habits she built up to ward off the effects of that trauma.
So yeah, smoking can communicate a lot of things about a character, such as:
self loathing
self destruction
poor rolemodel
anxiety
decline
old-fashionedness
bigotry
hypocrisy
toxicity
over-seriousness
hedonism
and many many more!
As far as for replacements for smoking, have you ever thought of toothpicks? they don't sound that cool but the character Grandma Dowdel from the book "A Year Down Yonder" was that she always kept a toothpick in her mouth that she could flip it forward with her tongue to pick her teeth. When I read that as a kid I thought it was really badass and it's something about the character that has stuck with me for years. Toothpicks can be an interesting visual that can carry their own symbolism, but that symbolism is something you can invent as a writer because there isn't a cultural stigma.
(sorry for the essay but this is a really interesting topic to me)