右键单击时如何将Select Option type子菜单添加到firefox？

通过分配ID给父parentId菜单并设置给子菜单，它们显示为父菜单的子菜单。

参考：menus.create()

例子：

browser.menus.create({
  id: "radio-green",
  type: "radio",
  title: "Make it green",
  contexts: ["all"],
  checked: false
}, onCreated);


// submenu
browser.menus.create({
  id: "sub1",
  parentId: "radio-green",
  type: "radio",
  title: "Submenu",
  contexts: ["all"],
  checked: false
}, onCreated);