You can't, basically.
You can write a Java Action that does the retrieval for you.
Within Studio Pro, you'll need to have the type of entity defined beforehand, otherwise Mendix has no idea what to do with the object.
You can retrieve a list using the MxObjectType CompleteName as input as such:
XPath<IMendixObject> xpath = XPath.create(getContext(), completeName);
List<IMendixObject> objectList = xpath.all();
return objectList;