Not sure I understand you correctly, but Bitwarden can do this (it's the 'passphrase' option).
"Oct 9 - This is in the next release for various apps." [1] the PR is from Oct 6 [2].
It is a very basic implementation as of now. The wordlist is English-only, and it doesn't have a minimum character account so it contains 'words' such as 'aa' and 'aaa'.
[1] https://community.bitwarden.com/t/add-an-ability-to-generate...
The PR discusses how the original word list that was referenced was changed out to the better long word list from https://www.eff.org/dice .