The Splitter should be doing that for you. Can you maybe take a screenshot of your pipeline and a separate one of the Splitter configuration that you were trying at the time. We can take a look and try to figure out what is going on.
Note that when building a pipeline, you’re trying to setup the different stages of processing that will be applied to the data that is flowing through it. There’s not really any looping going on. So, in your case, you’re receiving the data, maybe validating it, and then doing the REST POST. The Splitter is needed to reshape the data flow to expand the single input doc into multiple output docs that can go through the remaining stages of the pipeline.