How to set environment variables in SAP PO

Hello Experts,

There is an EMP based API query which contains 'TEST' script(which determines the response no of EMP to be triggered in batches) and 'Environment variables(batched_persons_0,batched_persons_1, etc.).

This EMP API calls another API with batch variables(batched_persons_0,batched_persons_1, etc.).

screenshot-2019-10-29-at-72702-pm-1.png

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How do we implement the same in SAP PO.How can environment variables be set and retrieve the appropriate 'batch_persons_x' to eventually call next interfaces.

Please suggest. Advance Thanks!