Check out the latest version of the free material-authoring tool.
Quixel also noted that the release marks the largest Smart Material addition to date with 100 new Smart Materials. Also, the update provides the ability to control the visibility of the parts of a model based on individual texture sets in Mixer’s viewport.
A new Flatten Mix feature allows users to merge all the layers in a Mixer project down into the individual texture maps for each texture set. There's more, of course.
Mixer 2021.1 is now available for free on Windows and macOS, in beta. Find more details here.