Oh, it's possible to attach the benchmark rating to a specific item. in my case I'm using https://schema.org/AggregateRating for that (since one meta benchmark result consists of several benchmark results). And the specific item is then just a Product, which is okay.

But how would you express that you have a list of those aggregate ratings, which are ordered on the same dimension? In general I'm struggling with how to create lists with the schema, and I'm not aware of them being used anyway. I might miss something.

But I think https://github.com/schemaorg/schemaorg/issues/2405 would cover it, a benchmark could be expressed as a ranked list type of a guide. It being an open and recent issue makes me think that probably it's really not possible to express yet.

Edit: I completely missed that this might already be merged, https://schema.org/Guide. I just missed it in the Changelog! It's part of the pending section.