What happens to your old wallet when you reconstitute your private keys on a new cold wallet? I'd like to move over to a bitcoin only wallet. I'd add a passphrase to the new wallet for an additional layer of protection.
Nothing since it'll be a different wallet since adding a "
BIP39 passphrase" would change the entire hierarchy of keys.
It wont derive the correct private keys from your old Bitcoin wallet.
That's assuming that you meant "
BIP39 Passphrase" and not just the "
Passphrase" for wallet encryption.