Can you please add a feature like this :)
For an unknown call (the telephone number is hidden) Boldbeast Recorder set the telephone number as 00000000.
By default all calls will be recorded.
You can set the "Rule to Auto Record Calls" option to Include List, therefore only calls whose telephone number are in the list will be automatically recorded. If you add 00000000 into the list unknown calls will be automatically recorded also.