Using created variables without PHP

I'm creating a string variable in my own custom action using the "new variables" procedure. This variable has the path of a page I want to redirect to. If I have PHP module enabled, I can then use the Path Redirect action along with echo $my_variable to redirect to the correct page. That works.

But, it seems like I should be able to load this variable without needing PHP. I notice that if I use the Load Node by ID action, it creates a variable that can then be loaded by actions such as Set Content Title without using PHP. (In a dropdown box in the Arguments fieldgroup) I've looked through the code for those actions, but I can't figure how Load Node by ID or Set Content Title are different from my module. How is it possible to have a variable that is accessible without PHP?

Thanks,
Wayne.