wf-uncomplete.js

const descendants = WF.currentItem().getChildren().flatMap(function getDesc(item) {
  return [item, ...item.getChildren().flatMap(getDesc)];
});

const completed = descendants.filter(item => item.isCompleted() && !item.isReadOnly());

if (completed.length === 0) {
  WF.showMessage("No completed items found.", false);
} else {
  WF.editGroup(() => completed.forEach(item => WF.completeItem(item)));
  WF.showMessage(`Uncompleted ${completed.length} item(s).`);
  setTimeout(WF.hideMessage, 5000);
}