In your Test Cases, If some of the Test Data is fetched dynamically from an API Endpoint, we might need to save the Test Data temporarily to use it in subsequent Test Steps. 
We can see how to store Run-time Test Data from REST API Steps in Testsigma in the following article - Storing Test Data from REST API Response in Testsigma

We will be sending a GET request to https://app.testsigma.com and saving the value of the key 'Server' from its Response Header as shown in the first step of this example - REST API steps with normal Test Steps - Example

Assume that the value of the key 'Server' is 'Apache/CentOS 4.3.6'.

Let us see how we can use the previously saved Run-time Test Data in a REST Test Step now.