Should all test cases be reusable and in the test suite? or are there scenario's where you would want to create a specific test case for a single user story? (or a combination of both)

i.e. a bug was solved for a specific OS. In this case I would actually like to test that specific OS and maybe one extra OS and focus mostly on the bug testing. Should you use a generic test that covers way more scenarios or could you just copy/create a test for this specific user story and use this as a throw-away functional test?

Other scenarios I could imagine are i.e. partial functionality or single time edge cases.

I tried googling for answers, if anyone could give me a source as to how this would work, that would be great.