Function cmd_key_set_exportability 

pub async fn cmd_key_set_exportability(
    client: &VtaClient,
    key_id: &str,
    exportable: bool,
) -> Result<(), Box<dyn Error>>

Mark a key as releasable, or refuse every future export of it.

exportable is required rather than defaulted and there is no toggle: the state is absolute, so re-running a command whose output you did not see lands where you asked rather than undoing it.