Matyas, Thank you for contacting Okta. The Okta platform currently supports only one Yubikey per user account.
I encourage you to file a feature request in the Okta Community. Once a feature request is submitted it is visible to other Okta admins, who can vote on it. Using this method will allow you to monitor your request throughout the process.
To file a feature request in the Okta Community: 1. Browse to https://support.okta.com 2. Login with your Okta credentials 3. Scroll to “Request Features” and click the “Go to Ideas” button 4. Click on the “Post Idea” button 5. Complete the form.