how to display student final grade in certificate
@111, there are templates which are used to render a certificate. These templates use the Mako templating language which allows adding embedded Python code (example). So you could import and invoke the appropriate method to show any custom information stored in the platform.
This would be best done inside an overriding template within a custom comprehensive theme to avoid modifying the platform code directly, which can cause issues when upgrading to a newer Open edX release.
Btw, Open edX doesn’t attach any special meaning to the grading categories and hence “final grade” is just one of the grading categories and nothing more.
Please let me know if you have any questions.