The Casa app uses an HD (hierarchical deterministic) key, which generates a new address with each transaction that's made.
Can I whitelist an address with an exchange?
Some exchanges offer the ability to whitelist a withdrawal address for additional security (Swan, Kraken, Coinbase, Gemini, etc.).
Each address in the Casa app continues to be valid even after it has been used and the app is showing you a new address, so it's fine to whitelist a Casa deposit address with the exchange and make multiple withdrawals to the same address, even though the app may show you a different deposit address.
Note: As an exception to the above, please keep in mind that if you ever transfer funds to a new keyset in your Casa app in what we call a key rotation, which you may do if, for example, you want to replace a hardware device in the future, you should not send to any addresses from before you rotated the key, since they would then be part of your old keyset and you would have to transfer the funds to the new keyset before you could send it. You should update your address wherever you have stored it to an address from your new keyset instead.