Can you set up a current wallet using a new signing device and at the same time add a passphrase to this new wallet? Like, basically, can you add a passphrase to a seed phrase that’s already been generated? Thanks.
If you want to add a passphrase and extend the words, you can not do that to your seed phrase that has been generated already without no passphrase added. You will ned to create a new wallet to add the passphrase. But before asking this question, you can do some findings about it on a wallet that supports passphrase. You will only see on your wallet that passphrase can only be added to new seed phrase that you just want to generate.
You can add as many different passphrases to your seed phrase as you want. But: each of them creates a new wallet. If that's what you want: go for it.
Keep in mind that using the same seed on more than one device generally increases the risks. It's usually recommended to create a new seed.
I take "signing device" as hardware wallet and "established wallet" as the wallet within a client connected to your hardware wallet, no?
Most wallets don't do that since the "Master Private Key" of the signing device with a passphrase will be different than the one without a passphrase.
Some hardware wallets use that as feature (IIRC, "hidden wallet" or something) but it's still not combined with any instance of the same wallet that has a no passphrase or different passphrase.
But it's theoretically doable if the client and hardware wallet can support multiple master keys.
Please tell the hardware wallet's model and the client (wallet) where you connected it if you want to get more accurate answers.
Misunderstandings like that are why I think that "passphrase" is a poor term. A seed phrase "passphrase" is not a passphrase. It does not give you access to the wallet. It is nothing like a passphrase.
The term "seed phrase extension" is much more accurate. Using that term instead of "passphrase" would eliminate a lot of confusion.
You can import a your seed phrase into any other wallet, but you cannot add a passphrase or extension to the already existing seed phrase, not that it is possible but you will be creating another different wallet entirely and the funds on the existing wallet will need to be transferred to that wallet with pass phrase.
I agree that the term pass phrase is kind of misleading but with the rate at which many wallets uses it, its better it is added in explaining to newbies to avoid further confusion when they got to see them on wallets.
Also I do somehow I think it is a passphrase to the seed phrase it is added upon, although technically its not because having alone is useless but you definitely need it to go through that wallet and if not you will be recovering a different wallet