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

group-export.jsx

// list of number index
var validLayers = [];

// list of list of active layer index
var combos = [];

// whether to export
var runExport = false;


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


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

    SavePNG(docName + '-' + i.toString() + '.png');
  }
}

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

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

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

  if (validLayers.length == 0){
    for (var i=0;i<layers.length;i++){
      if (layers[i].layers !== null){
        console.log(i, layers[i].name);
        validLayers.push(i);
      }
    }
  }

  console.log(validLayers);

  if (runExport){
    if (combos.length > 0){
      // if combos is defined
      exportByCombos();
    }
    else{
      exportByLoop();
    }
  }
}

ExportLayers()