By "complexity" I meant that they are "opaque" to me and somewhat not tied to and identity (be it email or username). Maybe it's me being inept, but I used them once or twice just for fun in Bitwarden and now I can't find them anywhere in my vault.

https://community.bitwarden.com/t/special-vault-search-keywo...

Maybe it's just a Bitwarden issue.

The 2FA issue isn't such for me. As I explained in a different comment, 2FA pins are copied automatically and are thus just a "ctrl+v" away.