I really don't think you'll see this built-in to the program. This is pretty much what the scripting functionality in mIRC is designed for.
A simple script to do what you want would be the following:
alias oneliners { window -odl +l @oneliners | loadbuf -rl @oneliners $scriptdir\oneliners.txt }
menu @oneliners {
lbclick:scid $window($lactivewid).cid | window -a $lactive | editbox -a $line(@oneliners,$1,1)
}
Just add your one liners to a file called oneliners.txt in the same directory as your script and type /oneliners to load the window. Change "editbox -a" to "say" if you just want it to hit enter automatically
As a sidenote, you could bypass the whole window thing and simply bind your one liners to function keys on your keyboard. You could easily change them in your aliases:
f5 say Hello everybody!
f6 say Bye bye!
f7 say Thanks, you are a nice person too.
Then just hit f5, f6, or f7 to send those messages. You can add more, just see /help function keys
