Adding an extra layer of security to your hardware wallet is possible using the passphrase feature.

The passphrase is an additional phrase on top of your recovery words.
One benefit of this is that if someone were to attain your recovery words, they would still need your passphrase to access your wallet.

Your passphrase can be any length and is made of letters, numbers, or special characters.

On a Ledger hardware wallet, you attach the passphrase to a pin. This means you will have two pins on your wallet. One pin will access your funds backed by your recovery words. The second pin will access your funds backed by the recovery words plus the passphrase.

Here is a more in-depth article by Ledger on passphrases: https://www.ledger.com/academy/passphrase-an-advanced-security-feature

If you want to set up a passphrase on your Ledger here are the instructions: