[GraphToolKit] Would it be possible to define type as variable/constant even if they are not specifically defined in a node

I currently have the following structure which work correctly. But now I want to support a list as a potentially entry but as my node is taking an object there is currently no type of List<ExposedReference<Character>> existing in my graph which means that I need to create a dummy node with this type to be able to create a variable that holds my data.