Jonah,
Yes, grouping them is possible. Maybe you have worked on certain types of projects? (i.e. kitchen development projects, garage demolition projects, garden renovation projects, etc.) That would be a good way to group them logically. But frankly, since you are going to show this to your supervisor anyway, why not discuss it with him/her to see what you can come up with. After all... if your supervisor agrees that "this is the way we did it" then PMI will be happy to accept it.
Generally, PMI is seeking confirmation that you have indeed managed projects. They don't want to see and review every single, individual project and if they are small, and similar and grouping them makes sense then go that way.