Do you mean you would like manually add new user and that `unique code` from backend user creation page?

But this `unique code` will be only show on their user profile, other user can't have the permission to view it?

No, I'm creating discount program and want assigned for all my users individual code (discount code number). This code will be generated for all users which registered users and new users.
I want have field where i can generate this code, and this field (this code) will be visible in user profile page but not visible in registration form.

Currently we do not have this such of custom field allow to generate random unique code during registration or automatically create for existing user.

Having said that, if you require us to perform the customization for you, you can always request for a quote from us at https://crm.stackideas.com and select "Customizations" . Our sales person would be glad to send you a quote for the customizations that you have requested.