The window where you can enter a function in the set properties is so small that when you enter a simple equation a scrollbar appears which is larger than the window itself.
The window can only be enlarged sideways, multi line windowd doesn't appear to be possible.
Duplicate of http://www.adrift.co/bug/18737
Also, the expression builder (http://www.adrift.co/bug/18323) would open a new window which would have a lot more space to display the expression.