The Swagger UI controls the ordering which does initially group by path segment which is why you’re seeing all your APIs under the api group, but doesn’t appear they order within that group.
You can create your own custom groups with the [Tag] attribute which should help with discovery, these also allow you to group APIs in the metadata page as well.
You could try reordering the APIs in the ApiDeclarationFilter where you can try reordering the Paths OrderedDictionary where your APIs are defined which may have an effect in Swaggers UI.