The adblocker Wipr has recently added something beyond the Content Blocker API with Wipr Extra. I only found it because I had forgotten to switch to AdGuard on my office Mac, and Wipr Extra showed up in an update. Lots of restrictions and caveats though about what it can and can't do. Some details at

https://giorgiocalderolla.com/wipr-faq.html#what-is-wipr-ext...