That's how I find them also; or wait until you are adding keywords -- Lr will throw up options from your list -- you can then find/delete them. Not sure you need to worry about finding and deleting; they usually surface at sometime . If the k/words are not attracted to any photo you can find them with the Lr smart collection 'without keywords' --- if not there then just a make a smart collection to suit.
All windows key boards have an "Alt" key --- coachejp may have been confused with Alt/Opt typing. Too much like common sense for different companies to have the same keys lol; or programs to use the same k/board short cuts