Feature request? Specify operation parameter as schema

[Miradorn]

Maybe this is already possible and I'm just missing it, but basically what i need is:

Specify an operation which has a oneOf for parameters, e.g. it either has a slug parameter XOR a identifier and scope parameter.
As I see it there is currently no way to do this while it seems to be supported by OpenApiSpec itself.
The main problem probably is that the schema is always "automatically" created from the parameters. Maybe there is an easy way to bypass that if the parameters are already specified as a schema?

Thanks for any help!