I record the network traffic via HTTPS Test Script Recorder. There are multiple requests getting captured.
Is there a way to categorize the requests that get triggered in parallel or sequentially? That is, how to understand which requests are being sent in parallel? Knowing this can help in placing those under a Parallel Controller.
You can figure that out by inspecting request start times in the View Results Tree listener, those which start within the same second or before previous one completion are a subject to parallel execution.
As of now there are 2 types of requests which are being executed in parallel:
Embedded resources (which you shouldn't be recording anyways, you should let JMeter download them by ticking the relevant box under "Advanced" tab of the HTTP Request Defaults).
Don't forget to add HTTP Cache Manager so the resources won't be re-downloaded on subsequent requests/iterations.
AJAX requests. These guys cannot be handled by JMeter at all, you can record them, but they will be replayed in sequential manner. JMeter cannot execute client-side JavaScript hence you will need to handle them manually