Modifying an existing script to suit new objectives

@andrewh85004476 

Here is an updated version that will automatically open the PSD files, which hopefully achieves what you wanted in a slightly different way.

/* 
Stack 4 Number of Document Sets to Layers - Top Level Folder.jsx
v 1.0, 18th July 2023 - Stephen Marsh

This script requires input files from a single folder to be alpha/numeric sorting in order to stack in the correct set quantity. 
*/

#target photoshop

if (!app.documents.length) {

    try {

        // Save and disable dialogs
        var restoreDialogMode = app.displayDialogs;
        app.displayDialogs = DialogModes.NO;

        // Main script function
        (function () {

            // Select the input folder
            var inputFolder = Folder.selectDialog('Please select the folder with files to process');
            if (inputFolder === null) return;

            // Limit the file format input, add or remove as required
            var fileList = inputFolder.getFiles(/\.(png|jpg|jpeg|tif|tiff|psd|psb)$/i);

            // Force alpha-numeric list sort
            // Use .reverse() for the first filename in the merged file
            // Remove .reverse() for the last filename in the merged file
            fileList.sort().reverse();

            var setQty = 4;

            // Validate that the file list is not empty
            var inputCount = fileList.length;
            var cancelScript1 = (inputCount === 0);
            if (cancelScript1 === true) {
                alert('Zero input files found, script cancelled!');
                return;
            }
            // Validate the input count vs. output count - Thanks to Kukurykus for the advice to test using % modulus
            var cancelScript2 = !(inputCount % setQty);
            alert(inputCount + ' input files stacked into sets of ' + setQty + ' will produce ' + inputCount / setQty + ' output files.');
            // Test if false, then terminate the script
            if (cancelScript2 === false) {
                alert('Script cancelled as the quantity of input files are not evenly divisible by the set quantity.');
                return;
            }

            // Select the output folder
            var outputFolder = Folder.selectDialog("Please select the folder to save to");
            if (outputFolder === null) {
                alert('Script cancelled!');
                return;
            }

            // Set the file processing counter
            var fileCounter = 0;

            // Loop through and open the file sets
            while (fileList.length) {
                // Sets of N quantity files
                for (var a = 0; a < setQty; a++) {
                    try {
                        app.open(fileList.pop());
                    } catch (e) { }
                }

                // Set the base doc layer name
                app.activeDocument = documents[0];
                docNameToLayerName();

                // Stack all open docs to the base doc
                while (app.documents.length > 1) {
                    app.activeDocument = documents[1];
                    docNameToLayerName();
                    app.activeDocument.activeLayer.duplicate(documents[0]);
                    app.activeDocument = documents[0];

                    // Do something to the stacked active layer (blend mode, opacity etc)
                    // app.activeDocument.activeLayer.blendMode = BlendMode.MULTIPLY;

                    app.documents[1].close(SaveOptions.DONOTSAVECHANGES);
                }

                ////////////////////////////////// Start doing stuff //////////////////////////////////
                // app.doAction("Daytime Flash Layer", "01. CP General");
                ////////////////////////////////// Finish doing stuff //////////////////////////////////

                // Delete XMP metadata to reduce final file size of output files
                removeXMP();

                // Save name + suffix & save path
                var Name = app.activeDocument.name.replace(/\.[^\.]+$/, '');
                var saveFile = File(outputFolder + '/' + Name + '_x' + setQty + '-Sets' + '.psd');
                // var saveFile = File(outputFolder + '/' + Name + '_x' + setQty + '-Sets' + '.jpg');

                // Call the save function
                savePSD(saveFile);

                // Close all open files without saving
                while (app.documents.length) {
                    app.activeDocument.close(SaveOptions.DONOTSAVECHANGES);
                }

                // Increment the file saving counter
                fileCounter++;


                ///// Functions /////

                function savePSD(saveFile) {
                    psdSaveOptions = new PhotoshopSaveOptions();
                    psdSaveOptions.embedColorProfile = true;
                    psdSaveOptions.alphaChannels = true;
                    psdSaveOptions.layers = true;
                    psdSaveOptions.annotations = true;
                    psdSaveOptions.spotColors = true;
                    // Save as
                    app.activeDocument.saveAs(saveFile, psdSaveOptions, true, Extension.LOWERCASE);
                }

                function docNameToLayerName() {
                    var layerName = app.activeDocument.name.replace(/\.[^\.]+$/, '');
                    app.activeDocument.activeLayer.name = layerName;
                }

                function removeXMP() {
                    if (!documents.length) return;
                    if (ExternalObject.AdobeXMPScript == undefined) ExternalObject.AdobeXMPScript = new ExternalObject("lib:AdobeXMPScript");
                    var xmp = new XMPMeta(activeDocument.xmpMetadata.rawData);
                    XMPUtils.removeProperties(xmp, "", "", XMPConst.REMOVE_ALL_PROPERTIES);
                    app.activeDocument.xmpMetadata.rawData = xmp.serialize();
                }

            }

            // Restore saved dialogs
            app.displayDialogs = restoreDialogMode;

            // Open the stacked PSD files
            var thePSDfiles = outputFolder.getFiles(/-Sets\.psd$/i);
            // thePSDfiles.sort.reverse();
            thePSDfiles.sort();
            for (var i = 0; i < thePSDfiles.length; i++) {
                app.open(File(thePSDfiles[i]));
            }

            // End of script notification
            app.beep();
            alert('Script completed!' + '\n' + fileCounter + ' combined files saved to:' + '\n' + outputFolder.fsName);

        }());

    } catch (e) {
        // Restore saved dialogs
        app.displayDialogs = restoreDialogMode;
        alert("If you see this message, something went wrong!" + "\r" + e + ' ' + e.line);

    }
} else {
    alert('Stack 4 Number of Sets:' + '\n' + 'Please close all open documents before running this script!');
}

Hmm, that code looks strangely familiar!

First, change:

var setQty = 2;

From 2 to 4.

The easiest way isn't exactly what you are requesting... Let it save out and close the PSD files as the script is designed to do. Then open all the PSD files again. This could be automated.

If you need the action to run afterwards on open, disable/remove it from the script and have it run on open or re-saving via Batch, Image Processor, Image Processor Pro or even Script Events Manager.

The script would probably need major rewriting to keep documents open. Hard for me, perhaps not challenging for others though.