You need to set your DataView to “listen to widget” so that it listens to the Listview showing your entity1. Within this dataview, you can now have a second dataview, showing your entity2 (via association).
When reading your other post about associations, it seems like many ToDos belong to one project (*-1 association). In this case, your dataview on the right side need to contain a widget that is able to show a list of objects (datagrid, templategrid or listview) because you might have multiple ToDos per project.