Got it. Scoped API keys are generated in the API libraries and are not stored on the Typesense-server-side. So the only way to revoke a scoped API key is by deleting the parent API key that was used to generate it.
Given this, one way to achieve what you're looking to do is to create one parent key per org, then generate a scoped API key for each org based on their respective parent key. Then when a user's org membership changes, you can revoke the parent key of the org, generate a new parent key and then use that parent key to generate a new scoped API key.
This way, the old scoped API key that the ex-user might have will no longer work.