[bravejohn]

but this way, when I change to other mob to do damage, when I will press again this macro it will set focus the target I am damaging, and cast Polymorph to that target

It is easy to work with 2 macros

#showtooltip
/clearfocus [@focus,dead]
/focus
/cast Polymorph

and then
#showtooltip
/cast [@focus] Polymorph

but the point is to avoid using a second keybind,as I already have plenty :P