Yes. You can cancel your Study.com membership while your assignments are being graded, and it will not affect your ability to receive a grade or request a transcript once grading is complete.
However, if your grader requires revisions or you decide to resubmit an assignment to get a higher score, you’ll need to have an active Study.com membership to make that resubmission.
In short, you’re free to cancel your membership at any time without losing access to completed grades or transcripts — just keep your membership active if you might need to revise or resubmit any pending assignments.