How can i add a submenu to a custom menu of another plugin?

Always happens. I ask and immediately find the answer.

The answer is in the 2nd plugin add a “priority” of 11 to the add_action command. This plugs that submenu right in there.

Like this: add_action('admin_menu', 'admin_submenu', 11);

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)