Marker Split.jsx

// Splits selected layers based on markers

// Adapted from: https://community.adobe.com/t5/after-effects-discussions/script-that-splits-a-layer-into-multiple-layers-at-marked-points/td-p/13625174

var comp = app.project.activeItem;
var layers = comp.selectedLayers;
var all = 0;
var stop = layers.length;
if (layers.length == 0) {
    layers = comp.layers;
    all=1;
    stop = layers.length+1;
}

app.beginUndoGroup("Split layers on markers");

if (layers.length > 0) {
    for(var i = (all==0) ? 0 : 1; i < stop; i++){

        // Create a copy of original and hide
        copy = layers[i].duplicate();
        copy.audioEnabled = false;
        copy.enabled = false;
        copy.label = 0;
        copy.moveAfter(layers[i]);

        var myLayer = layers[i];
        for (var i = 1; i <= myLayer.property("marker").numKeys; i++) {
            var newLayer = myLayer.duplicate();
            newLayer.inPoint = myLayer.property("marker").keyTime(i);
            newLayer.name = myLayer.property("marker").keyValue(i).comment;
            if (i < myLayer.property("marker").numKeys){
                newLayer.outPoint = myLayer.property("marker").keyTime(i+1);
            }

            // Cause duplicates to be created below original layer
            //newLayer.moveAfter(comp.layer(myLayer.index + (i-1)));

            // Cause duplicates to be created above original layer
            if (i>1)
                newLayer.moveBefore(comp.layer(newLayer.index - (i-1)));
        }

        if (myLayer.property("marker").numKeys > 0){
            myLayer.outPoint = myLayer.property("marker").keyTime(1);
        }
        if (myLayer.inPoint == myLayer.outPoint)
            myLayer.remove();
    }
}

app.endUndoGroup();