End Hold & End Split

(function() {
    var comp = app.project.activeItem;
    if (!comp || !(comp instanceof CompItem)) {
        alert("Please select a composition.");
        return;
    }
    var layer = comp.selectedLayers[0];
    if (!layer) {
        alert("Please select a layer.");
        return;
    }
    app.beginUndoGroup("Apply Time Remapping");

    // Enable time remapping for the layer
    layer.timeRemapEnabled = true;
    var timeRemap = layer.property("ADBE Time Remapping");

    // Add a keyframe at the current time
    var currentTime = comp.time;
    var keyIndex = timeRemap.addKey(currentTime);

    // Make the keyframe an ease-in keyframe
    var easeIn = KeyframeInterpolationType.BEZIER;
    timeRemap.setInterpolationTypeAtKey(keyIndex, easeIn, easeIn);

    // Add a hold keyframe immediately after
    var holdKeyIndex = timeRemap.addKey(currentTime + comp.frameDuration);
    var hold = KeyframeInterpolationType.HOLD;
    timeRemap.setInterpolationTypeAtKey(holdKeyIndex, hold, hold);

    // Remove the last keyframe
    var lastKeyIndex = timeRemap.numKeys;
    timeRemap.removeKey(lastKeyIndex);

    app.endUndoGroup();
})();