The only option I see is to change the size of the code itself. However, this is probably not enough. Changing the resolution of your screen when using Greenfoot is probably also not a great way of dealing with this issue. You may send an E-Mail to "support@greenfoot.org" in case no one from the Greenfoot Team sees this discussion. Maybe they can add such an option for a future version of Greenfoot or show you a way how it is possible for you to do that in some other way I don't know about.