@Alexis_Odysseos thanks for asking about this -- I tried this out and I can reference configVars in a postgreSQL query, in a JS query, and in the variables of a GraphQL query for example (below):
What type of query are you aiming to reference config vars from? Some screenshots of where you're trying to reference or more detail on the type of resource, and use case will help me pinpoint more context (pun not intended) on this for you!