After the Search API Step, you can create a Data Source Test Step for either XML or JSON (or scripted with Groovy)
https://support.smartbear.com/readyapi/docs/testing/data-driven/types/xml.html
https://support.smartbear.com/readyapi/docs/testing/data-driven/types/json.html
https://support.smartbear.com/readyapi/docs/testing/data-driven/types/groovy.html
you will have to map the fields from your Search API to this step and once the Search Step is completed, it will fetch all the necessary nodes from and create them as data rows
you will then have your Update API request and for each of the request parameters use the GetData function to read the Data source
you can then perform a Read to assert on that the Update was valid.
Then Create a Data Source Loop Step using the Data Source Test Step and the Update API as the step to start the loop on
