要使Up/Down键具有与Tab键相同的功能，最简单的方法是使用React.useEffect挂钩。这将允许您在按下Down键时调度一个keypress事件。
更改这些行：

const handleKeyDown = (event) => {
  if (event.key === "ArrowRight" && !open) {
    setOpen(true);
  } else if (event.key === "ArrowLeft" && open) {
    setOpen(false);
  } else if (event.key === "ArrowDown") {
    //event.dispatchEvent(new Event("keypress", { keyCode: 9 }));
  }
};

对此：

React.useEffect(() => {
  const handleKeyDown = (event) => {
    if (event.key === "ArrowRight" && !open) {
      setOpen(true);
    } else if (event.key === "ArrowLeft" && open) {
      setOpen(false);
    } else if (event.key === "ArrowDown") {
      event.dispatchEvent(new Event("keypress", { keyCode: 9 }));
    }
  };
  document.addEventListener("keydown", handleKeyDown);
  return () => {
    document.removeEventListener("keydown", handleKeyDown);
  };
}, [open]);

这将使向上/向下键具有与Tab键相同的功能。