This doesn't work when we input long expressions. And as Jim wrote about a formatting feature in earlier version he seems to be in need for an input solution.
Furthermore moving the margin won't help if he wants his definition be seen complete in a printed report.
Changing paper orientation to landscape and changing the fontsize to something smaller (but this affects the whole worksheet!) are workarounds which may be useful in some situations but are nevertheless not adequate. The same goes for breaking an assignment into parts like part1:=a+b+c part2:=e+f+g variable:=part1 + part2.
It was already often claimed here - we need linebreaks for input and output of expresssions.