Access Model Workspace Variable through C API

Model workspace variable are per definition non-tunable. However, variables (both simulink signals and parameters) in model workspaces can be still of type SimulinkGlobal or ExportedGlobal. In the generated code, these variables become included in the struct with other tunable parameters. But when I generate code with C API, they do not appear in rtDataAddrMap where they can be accessed by C API. Is there any possibility to do so?