Save to Files as...

// prompt for file name
var title = draft.processTemplate("[[safe_title]]");

var p = Prompt.create();
p.title = "Save as...";
p.addTextField("fileName", "Name", title + ".txt");
p.addButton("Export");

if (p.show()) {
   var fileName = p.fieldValues["fileName"];
   draft.setTemplateTag("file", fileName);
}
else {
  context.cancel();
}