I think it’s possible using extendScript. Have you played with velocity or speedAtTime values? Velocity is supposed to return the tangent vector value for spatial properties, like position.

I’m not sure if I understand your question, but if you’re extending the length of the Comp, you’ll need to loop through the layers and set the outPoint of each layer to the new length of the Comp. If you’re already doing that, can you provide a more concrete example, maybe posting the script?

Is this for a script, or an expression? If it’s a script, can you not set the width of the text layer, and have it break automatically?

Thanks for purchasing it. I’m not sure immediately how I would make it work over multiple layers, from a UI perspective. I’ve never encountered a timeline with 100’s of layers with markers. Are they all identical? Can you share some more information about this particular project?

I’m very late to this thread, but I just developed a script for AE that let’s you add, edit, delete, shift in time and copy any or all markers on a layer or a Comp. It’s called Marker Maestro and can be found here https://aescripts.com/markermaestro

Hope this helps someone.