This is a page from the Cascading Style Sheets Working Group Blog. Some other places to find information are the “current work” page, the www-style mailing list, the Future of CSS syndicator, and the issue list on Github.
Do you want to know how the CSS WG works? Fantasai has written about:csswg, An Inside View of the CSS Working Group at W3C.
:defined
to selectors L4 (Issue #2258)line-box-contain
(Issue #3199, Proposal) created a lot of interest, but time ran out on the call so those who wish to discuss further will organize a separate call to dive deeper into details.