You need to do outside Splunk GUI as GUI supports REST GET only.
So your client (postman) or curl.
An example using CURL with MySavedSearch which has ownership of admin user
curl -k -u admin:pass https://localhost:8089/servicesNS/admin/search/saved/searches/MySavedSearch -d title="MyNewSearch"
Please refer https://docs.splunk.com/Documentation/Splunk/7.2.6/RESTREF/RESTsearch
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