mapAsync for custom stage

I couldn’t find clear answer to my question so I’ve decided to post it here:
I have stream that must preserve order to ack appropriately on Kafka using Commiter (
This stream to some elements apply conditional flow based on predicate using custom stage described here:

As applied action is async I would like to run them similar to function that could be executed in .mapAsync with given parallelism level but preserve elements order.

Currently my impl look like below:

        .via(applyConditionalFlow) // here we're using custom stage that apply flow conditionally
        .map(res => res.originalMsg.committableOffset)

Is there a way to run applyConditionalFlow parallel with given by parameter parallelism level (similar to .mapAsync) with preserving order?