In TestPlanning, when synching the test cases and bring in testcases, there is a window that opens "Proceed with Synchronization", where you can check the box "remove the deleted folders/testcases from this schedule. "
When checking the box "Remove" and then click "Continue" the next window that comes is showing the result of the operation, there is no chance to undo the operation.
For a better experience the result window informing about what is added and removed from the scope should come with a "cancel" button that gives the user the chance to regret the operation.