When I started to create my website using Tempera Theme, everything is fine, I can add and remove the sub-menus. After a while when I tried to add more sub-menus, it does not work.
When I delete the existing sub-menu and add back, it no longer appear.
From forum it advise to configure the info.php and set the max_input_vars to bigger value. I have set to 5000 and reboot the server. I still facing the problem to add sub-menus/