I've been watching this solar youtube video to create a solar surface and I don't understand how he took 3 layers in the "Star Map" composition and made them into one layer on the "Sun" composition. What is this technique?
I just figured it out. In After Effects 2020 the technique is called layer grouping. This can be achieved by:
At the end of this. All your layers in the first composition have been grouped together into a new composition. The new layer is given the name you typed in option 3 above.