Found the Menu Editor has bug

When add new menu at menu editor, all the other menu is gone off.  Please help solve

if we create the new menu as shown in screen shot, https://pasteboard.co/JSpaqtf.png  , all the menu will be disappeared.

So what we can do to temporarily solve now is to create under sub menu  https://pasteboard.co/JSpbaLd.png , and then move to main menu, then the whole menu will not disappeared.