#showtooltip
/cast [mod:shift,@player] [@mouseover,exists,nodead] [] Holy Shock
That will let you mouseover both friends and enemies. If you only want to be able to do friends change exists to help.
Also, keep in mind that keybinds take priority over modifiers so you’ll need to unbind whatever conflicts you have on shift-key (by default SHIFT 1-6 are bound to Action Page 1-6)