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.
animation-direction
reverses an animation, the timing function goes in reverse
z-index
is *not* optional on page-margin boxes.
format()
in image()
for fallbacks, and where to register new subtypes.
display
shorthand, so that it is not accidentally reset by style rules setting the box type