Bip39 cli https://www.giantbomb.com/profile/blathayqvn/ While it utilizes BIP32 approach you may still import BIP39 seeds into Electrum wallet. Also aside from BIp32 There may be BIP44 Model which some wallet use with the generation of seeds. For words that have only 3 letters, there is absolutely no 4th letter. For example https://maximusbookmarks.com/story20304164/bip39-mnemonic-generator-python-bip39-npm-no-further-a-mystery-https-dzen-ru-bip39-phrase-com