How do I add more passphrases for GPG symmetric encryption?

Question

With GPG I can encrypt file symmetrically, as for example described here: How do I symmetrically encrypt a file using gpg?. On decryption it will show (among other lines):

gpg: encrypted with 1 passphrase

How can I add more than one passphrase on encrypting the file?

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Notes:

• I know it is possible to add multiple recipients in the asymmetric encryption.

• One can encrypt the file both symmetric and asymmetric at the same time. From the manpage of gpg:

  -e     Encrypt data. This option may be combined with --sign (for  a
         signed  and  encrypted  message),  --symmetric (for a message
         that may be decrypted via a secret key or a  passphrase),  [...]
  

• A message on the gnupg mailing list from 2004 indicates that it is not yet possible. Now almost 10 years later and this might not be correct anymore.

Answer 1

GnuPG still has not implemented the ability to add multiple passphrases for symmetric encryption.

Answer 2

Combine with using "ssss"
Split and Combine Secrets using Shamir's Secret Sharing Scheme.

Answer 3

Run gpg2 -c on it twice: first, the file you want to encrypt and second, the encrypted file.