You could create a separate element for the certificate (if you have programming knowledge) to achieve this.
In the meantime I created https://github.com/markn86/moodle-mod_customcert/issues/255.
I do work on this plugin in my spare time and there is already a huge backlog, so if someone wants to provide a patch feel free.
I will be going through the backlog for a whole week in December and will release a new version, not sure if this will make it in the release but will see.