Edit enum values from solution

I've created an enum in my language and a concept which uses this enum as property. Then I use this concept in another concept as child to get several enum members. Now I want to add additional enum members in a node of the sandbox solution. Is this possible? I've tried to write a setter in the behavioral aspect of the concept that encapsulates the enum but I can't access the enum (or any other of my enums) in the behavior aspect through enum/<name>/.operation. Is this a bug? Is there any other possibility to do this?