This is the base template:
For Shadowstep specifically it’d be
#showtooltip
/cast [@mouseover,exists,nodead] [] Shadowstep
Unless you’re doing it in pvp where it can get janky and you need the following
#showtooltip
/cleartarget [@mouseover,exists,nodead]
/cast [@mouseover,exists,nodead] [] Shadowstep
/targetlasttarget [@mouseover,exists,nodead]