My objective is to update a transaction table record while being confined to the SuiteQL API. Direct NetSuite access is unavailable, so I'm employing SuiteQL to retrieve records, and it's working effectively. just want to update the record but do not know how to do this one using endpoint please help to soort out this issue

You cannot update via SuiteQL, only SELECT.

Yep, read only. You need N/record to update.

I am an integration engineer with no prior NetSuite experience. We have successfully integrated NetSuite and can retrieve records. However, I now need to update records in NetSuite using the provided endpoint and valid token. Please guide me through this process

You can update records using Restlets, SOAP or REST.