Casa App uses an HD (hierarchical deterministic) bitcoin key, which generates a new address with each transaction that's made.
Can I whitelist an address with an exchange?
Some bitcoin exchanges offer the ability to whitelist a withdrawal address for additional security (Swan, Kraken, Coinbase, Gemini, etc.).
Each address in Casa App continues to be valid even after it has been used and Casa 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 Casa 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 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 that address, since it would then be part of your old keyset and you would have to transfer it 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.