When creating a node filter for a VFC in a VF or service, the value given must match the type of the property. There is nothing to indicate to the user what type that value should be, similarly the error generated if an invalid type is entered does not help. 

For list/map/complex types the static value free text field should be replaced with an appropriate input for the given type

Similarly, where the source is selected to be another property rather than a static value, selection of only properties with same type should be allowed