I just went down a rabbit hole on this a few days ago, so it's fresh in my mind. As far as I can tell, there isn't a bestselling novelist named Cho Yoon Woo active in the English-language market. When I first saw the name, I thought maybe it was a new Korean author being translated, so I checked the usual sources—the Korean Book Council lists, translation databases, major publisher catalogs. Nothing popped up.
It's possible it's a different romanization of a more familiar author's name, like Cho Yŏn-u, but that's a guess. Sometimes a popular webnovel writer uses a pen name that gets mistranslated. I did find a few scattered forum posts asking the same thing, mostly people who heard the name secondhand from a friend or saw it referenced vaguely in a comment. Leads me to think it might be a case of a name getting slightly mangled in transmission, like how 'Haruki Murakami' sometimes gets misremembered as 'Hiroshi Murakami'.
Whoever you heard it from might be thinking of Cho Nam-joo, who wrote 'Kim Jiyoung, Born 1982'—that was a massive bestseller. Or maybe the Korean author You-Jeong Jeong? Their thriller 'The Good Son' did really well. The 'Cho' surname is common, and 'Yoon Woo' could be a given name or even two separate names spliced together accidentally. Without a specific title attached, it's like looking for a ghost. My shelf of Korean fiction in translation is pretty deep, and that name just doesn't have a book next to it.