Visibility based on an attribute of referenced object

I have two entities. An entity, called Key, defines the name of the key and the expected data type for it; the other entity, called Values, references the Key and contains StringValue, DateValue, and DecimalValue attributes. When I author values, I am selecting Key via the reference selector and would like to change visibility of data entry fields of Values entity based on the type of the key. Unfortunately, when I try to define the editability rule based on expression, I do not see to have access to attributes of Key entity. What is the best practice solving such problem?
1 answers

For managing visibility via microflow for instance you could use the ‘ShowByCondition’ widget from the AppStore. For managing editability based on a microflow you could use the ‘EditableByCondition’ widget from the AppStore. 

Another alternative would be to store the key also on the values entity via an enumeration. Obviously not a best practice though. Would be best if Mendix implemented those widgets into the platform..