Ha, unfortunately Webflow’s redirects aren’t actually exposed as regex, even though the patterns hint at an underlying regex matching engine.
Your only option here is to do the redirect externally. That’s a bit of work, the approach I use is to proxy the site on cloudflare, and then use cloudflare’s redirect rules.
Note there’s a limit on Cloudflare free plan, I think it’s something like 25 redirect rules. But you can use it in conjunction with Webflow’s to handle just those special redirects that Webflow doesn’t support.