Can't see "Enforce strict scoping rules"

I have a radio button group in which I'm attempting to deselect a button. There are examples by Niall and others that I've copied, but it's not working, apparently because this.initValue is not being passed from MouseDown to MouseUp. It seems that deselecting "Enforce strict scoping rules" might solve the problem, but this parameter is missing from the application.

I'm running ADEP Designer version 10, and there's nothing about scoping in either File Properties > Defaults or File Properties > Run-time. Anyone have any idea why it's not there?

Thanks, Steve