How can I convert my Ed visa extension to a COVID extension before it expires?

You need documentation from your school saying you will stop studying and the date you'll end. Take that letter to immigration with you when you to apply for your Covid extension because you need to cancel your education extension first and then apply for Covid extension.

You can TRY to apply for a Covid extension. But be aware that an extension is not a promised one. Your application may or may not be approved.

You get the documents from your school saying you are finishing your study as of this date, go to your local immigration office, apply for cancellation of your current extension based on studying, then apply for a Covid extension immediately.

In case your application is not approved, you will be stamped for 7 days to leave the Kingdom. Be ready with Plan B.

General information for the Covid extension is here. Detail should be checked with your local immigration office.