If it's a preset, it should know to start at the beginning of the layer
Nope. Animation presets are always inserted at the current time - that is if they are not based on some fancy expressions that compensate. Same for copy&paste. Still, animation presets should apply to al lcurrently selected layers, so I'm not sure what you are doing or not doing to prevent it from working....
When I select the preset from the side panel, it deselects all of my layers. I then applied it to one layer to copy paste the animator to the others. Nothing. One to one worked, but to the wrong location.
Is there an expresssion that instructs multiple layers with similar content to animate at the inpoint?
I think you're going about this all wrong. This is a pretty easy process:
Create just ONE text layer, and animate it to taste.
Duplicate this layer, and change the text on the duplicated layer.
Move the duplicated layer on the timeline until its in point is at the desired point in time.
Repeat the steps above as necessary.
That's me - always thinking backwards! But I need to make a change after the fact to all of the text layers.
Not knowing what the term "change after the fact" entails, there could be two responses:
"So suck it up and get busy!"
"We'll need to know precisely what's wrong in the duplicated layers. There may be an alternate solution."
Since there are only 20 text layers -- a very small amount in a comp of even moderate complexity -- I favor the first response.
By "after the fact", I meant it is too late to plan ahead.
It's simple enough to copy and paste an animator from one clip to 20 others at once. I did that with the 'type on' text animation, but it placed all of the keyframes at the timeline marker and not the start of each layer. Nor I could not select all the text layers at once and apply the animation from the effects panel. Not sure if I should have been able to. When I dragged the effeect over to the clips, the layers were deselected.
Originally, I wanted to make one long bulleted text layer and animate each phrase to appear sequentially to a narration. Keyframed the heck out of it, but realized what a pain it would be to edit them afterwards. I suppose there is an expression, but I don't know what exactly I would pickwhip to.
How tough can it be to lasso the keyframes on each layer and move them to the times desired? That's all it takes!
So suck it up and get busy!
So what if you made a mistake? I bet you don't make it again.
You are overthinking this and trying to be overly efficient/ smart about the matter. 20 layers? That's kindergarten stuff that takes 5 minutes even if you need to re-create everything from scratch. I'd only be worried if I had to do this for hundreds of layers. Sure, everything can be automated using expressions just as well, but you need to provide much more info how you want it to work then. This could be as simple as something with thisComp.layer("XYZ").position.valueAtTime(time-inPoint), if all the layers have the same duration and keyframes and need to have the same motion just offset in time, on the otehr hand it could be infinitely more complex.
A client just left my shop reasured me that simplicity is usually best.