I hadn’t noticed this features introduction to the After Effects Beta till I saw this video from Creative Dojo.
This will clean up After Effect Timelines to now end, as you can basically add Track Mattes nodally, so you can add just one to a comp and use it for as many layers as you want, and if you save to an older version it will automatically add to all of the layers it is attached to.
This makes Track mattes the best of both world! OMG, need this for adjustment layers too, so they can be added selectively.
Wow, Adobe, this is such a cool addition.