The quickstart guide has an image of PPL page.
https://opendistro.github.io/for-elasticsearch-docs/docs/ppl/
There is a "Download" drop down button in the screen. I do not see that option. SQL query output has that Download button, but PPL does not. I am using 7.9 version of Amazon Elasticsearch server instance.
Ppl doesn’t support download yet, reporting features will be added to ppl soon on the query workbench. Please add an issue on the repo to track.