Loop an API call with JSON field

I have the above workflow - I have a GET Request that has a URL (and credentials) to pull data from an API. Unfortunately, the API limits data pulls to 300 records. I have several thousand records to pull. IN the API / JSON output, there is a field called “next”.

I need to loop that “next” field back into the GET Request, overwriting the original URL and keep looping until there are no more “next” fields. I did some research and saw that I need to use the Loop start, then create a table row to variable row to extract that ‘next’ field, then feed back into the GET Request as a flow variable? But the input is already taken by the loop start. How do I start the first call with the original API, then extract the 'next; field and insert back into the URL field of the GET node, and continually looping until complete?