Turns out if you try to save some time and use a certification for multiple courses, all the course options appear for the user in renewals.
I am running into this with the two courses I have for Fire Extinguishers. I have one long course and one short course on fire extinguishers, and I let my customer PUs choose which one to roll out to their team. What is confusing is now that I have the renewal widget front and center on the homepage for users, when they click on it, they see both courses. I do have enrollments locked, so in theory, they are only able to take the course they previously did, but it is still confusing.
I will also really run into this with harassment training. I made generic annual and biannual certs that meet multiple state requirements.

Soo now I suppose I have to create new certs for each course, then pull the data on who already earned it and when, and then assign the new cert. UNLESS someone has a better idea?? :)