I've checked this option in settings that says: "Registration requires administrator's approval:" in kentico10.
and in my custom registration web part I've unchecked Enable user after registration.
but I can't see unable users waiting for the approval tab.
as below picture.
It's because you checked the setting Registration requires email confirmation in Settings -> Security and membership
you need to unchecked this. since it's checked, system will send email to user after registration. while your email configuration has a problem, user can not received the confirmation link and it wont be worked.