If a stream is manually disabled (by unchecking Streams->Inventory->(Stream)->Live->Stream Active) or otherwise considered unhealthy (including an "Unknown" health-state), then it cannot be seen in the Streams->Configuration picker which is the only place where a Delete button is offered for streams.
If a stream is manually disabled (by unchecking Streams->Inventory->(Stream)->Live->Stream Active) or otherwise considered unhealthy (including an "Unknown" health-state), then it cannot be seen in the Streams->Configuration picker which is the only place where a Delete button is offered for streams.