Can I delete just one Assistive Technology from a use case in AMP?

You are not able to delete just one Assistive Technology, or AT, from one use case. If you delete a use case, all of the component AT use cases will be deleted. You can fully delete a use case, which would delete each of the ATs; You could also edit the use case section so that no use case tests for an AT, but that would eliminate that AT from every other use case as well. Finally, you can clear the contents of an AT, which would be the best alternative if you don't want the results of one use case's AT test weigh against your compliance.