Tips for golfing in Io
Higher-level function shorthand
This seems like a pretty interesting golfing point. E.g.

list(1,2,3)map(i,i+1)print

However, Io is pretty permissive on not specifying the counter; the map body can be used as a point-free function, as Io tries to fill in the operand of this expression. This can be golfed into

list(1,2,3)map(+1)print


Due to the helpful work of the language creator, you can even do this to reduces!
list(1,2,3)reduce(a,b,a*b)

Can easily be reduced into:
list(1,2,3)reduce(*)

(Unfortunately, I still haven't managed to understand how exactly this works, so I never managed to make the expression more complex.)