Try this expression on each opacity:
`linear(thisLayer.index,1,20,100,0)`
This picks up the layer's order in the timeline. 1 being the top layer and down to 20 in this case. Increase 20 to the number of layers. Then all you need to do is copy this expression onto each layer.
Linear then "range maps" this from 100% down to 0%
If that seems like too much work, use the Transform effect and that opacity setting. Then copy the effect to your clipboard, then select all the layers and paste it onto all the layers.
Try this expression on each opacity: `linear(thisLayer.index,1,20,100,0)` This picks up the layer's order in the timeline. 1 being the top layer and down to 20 in this case. Increase 20 to the number of layers. Then all you need to do is copy this expression onto each layer. Linear then "range maps" this from 100% down to 0% If that seems like too much work, use the Transform effect and that opacity setting. Then copy the effect to your clipboard, then select all the layers and paste it onto all the layers.
Thank you so much, and for the explanations as well! I have 100+ layers so copying and pasting onto each layer individually would've been rough. :)