To get the nested smart object layer names

It was a hint.

All information is in the json object.

You just need to extract it in the form you need.

For example

//////////////////////////////////////////////
function show_tree(json)
    {
    try {
        var s = "";

        show_layers(json.placed, json.layers, "");

        alert(s);

        function show_layers(placed, layers, level)
            {
            try {
                if (layers)
                    {
                    for (var i = 0; i < layers.length; i++)
                        {
                        var prefix = "Layer: ";
        
                        if (layers[i].layers) prefix = "Group: ";
                        if (layers[i].smartObject) prefix = "SmartObject: ";
        
                        s += level + prefix + layers[i].name + "\n";
                        
                        if (layers[i].smartObject) show_layers(placed, get_placed(placed, layers[i].smartObject.ID), "- " + level);
        
                        if (layers[i].layers) show_layers(placed, layers[i].layers, "- " + level);
                        }
                    }
                }
            catch (e) { throw(e); }
            }
        
        function get_placed(placed, placed_id)
            {
            try {
                if (placed)
                    {
                    for (var i = 0; i < placed.length; i++)
                        {
                        if (placed[i].placedID == placed_id) return placed[i].layers;
        
                        if (placed[i].placed) return get_placed(placed[i].placed, placed_id);
                        }
                    }
        
                return null;
                }            
            catch (e) { throw(e); }
            }
        }
    catch (e) { alert(e);  }
    }
        
//////////////////////////////////////////////
try {
    var r = new ActionReference();
    var d = new ActionDescriptor();
        
    r.putProperty(stringIDToTypeID("property"), stringIDToTypeID("json"));
    r.putEnumerated(stringIDToTypeID("document"), stringIDToTypeID("ordinal"), stringIDToTypeID("targetEnum"));
    d.putReference(stringIDToTypeID("null"), r);

    d.putBoolean(stringIDToTypeID("expandSmartObjects"), true);

    eval("var json="+executeAction(stringIDToTypeID("get"), d, DialogModes.NO).getString(stringIDToTypeID("json")));

    show_tree(json);

    alert(json.toSource());
    }
catch (e) { alert(e);  }