It would be handy if the generated reference documentation for the GTK and WPE ports would include one page with information about the JSON source format accepted for filter rule sets. It would be something similar to the following page: https://developer.apple.com/documentation/safariservices/creating_a_content_blocker?language=objc
I'm going to wait a bit more to see if anybody replies to the thread in the webkit-dev mailint list: https://lists.webkit.org/pipermail/webkit-dev/2019-March/030566.html If there is no reply in some weeks I will write the documentation myself from scratch =)