Additional properties for WorkflowDefinition / WorkflowInstance Entities

I am wondering if it's possible to have additional properties for the WorkflowDefinition and WorkflowInstance entities.

Currently, I am using Entity Framework with Postgres Persistence. Upon reviewing the default implementation in IWorkflowInstanceStore.cs, it appears that it enforces the usage of the default entity. Nevertheless, it seems that the only viable option is to add my data to a different table when registering a Definition or Instance and later perform a join to gather all the data.

Column Example: Enum DefaultErrorBehavior (1 = Fail, 2 = Retry every 5 minutes, 3 = send to sentry).

Am I missing something?