No, nothing like that is supported (or requested by any relevant RFCs, as far as I know). Can you describe the use-case in more detail? Correct me if I’m wrong, but multipart/form-data usage is not really related to size of the data to be POSTed.
I’d like to create a POST endpoint, using which I’d like to upload a large size image say 10gb. Would be using Amazon S3 multipart upload mechanism to implement the same through an action point.