Photopea export all group layers (folders) into separated PNG files.

group-export.jsx

function GetDocName(){
  var split = app.activeDocument.name.split('.');
  split.pop();
  var docName = split.join("."); 
  return docName;
}


function SavePNG(saveFile){
  var pngOpts = new ExportOptionsSaveForWeb; 
  pngOpts.format = SaveDocumentType.PNG
  pngOpts.PNG8 = false; 
  pngOpts.transparency = false; 
  pngOpts.interlaced = false; 
  pngOpts.quality = 100;
  activeDocument.exportDocument(new File(saveFile),ExportType.SAVEFORWEB,pngOpts); 
}

function ExportLayers(){
  var layers = app.activeDocument.layers;
  var docName = GetDocName();

  var numLayers = layers.length;
  var excludeLast = true;

  if(excludeLast) numLayers--;

  for (var i=0;i<numLayers; i++){
    for (var j=0;j<layers.length; j++){
        layers[j].visible = false;
    }
    layers[i].visible = true;

    SavePNG(docName + '-' + layers[i].name + '.png');
  }
}

ExportLayers()