"man zshzle" will tell you about special widgets. Basically, they're just user defined commands that instead of being called by a keystroke are called at particular points during editing. The test is just an ordinary zsh pattern, as used for globbing / file matching, so it's easy to extend... if [[ $BUFFER = (tasn|taxx|tmxx)' '* && $BUFFER != *\\* ]]; then
Nice. Yeah, this annoyance has been bugging me for years. I'll share this out to the TW community, I'm sure others will love this, too.