Hi Lisa,
I am not the author of any certificate 'block', just the activities (well I didn't create mod_certificate just maintained it after 1.9).
If you would like to see this in mod_customcert please create an issue at https://github.com/markn86/moodle-mod_customcert/issues and I will review the code there. I did notice it is using legacy code, so would probably require considerable changes in order for it to work with 3.2 onwards.