Not quite the same, but fish shell has programmable abbreviations. I type “tf<space>” and it expands that inline to “opentofu”. It use to say “terraform” before we upgraded; I didn’t even have to change the commands I type.

fish isn't POSIX though, I'm guessing ZSH can probably do something similar but command completion just isn't the same as being shortening "mkdir test" to "mkd test"