@Alexis_Odysseos got it, thank you for surfacing this! I've split this out into a new Feature Request post so we can track the request to allow accessing {{ retoolContext.configVars }} in the QueryLibrary. We can keep you posted there if this gets picked up by the eng team and implemented, and also track others' interest in it there.
@cosmick fyi circling back to confirm that the issue where {{retoolContext.configVars}} was not returning configuration variables when referenced from apps/queries was already fixed in Cloud and has also been back-ported in self-hosted v3.4.12 
Thanks again for posting about this!