you can double up on modifers eg.
#showtooltip
/cast [mod:shift,@mouseover,help,nodead] [mod:shift] Cleanse; [mod:alt,@mouseover,help,nodead] [mod:alt] Word of Glory; [@mouseover,help,nodead] [] Flash of Light
shift = Cleanse
Below are my personal macros I use for each class/spec. The purpose of them is to condense the number of physical keys you need to press by controlling which spell is cast via modifier (alt/shift/ctrl) and adding enhanced targeting capabilities where applicable.
I’ve included the keys I have them bound to but you can use whatever.