If you want to tie multiple projects together then you must use a "Controller" project. Basically, one of the projects with references to the others; either direct or indirect (where you'd reference a project that referenced a child project). After adding references to the projects to your controller project, you need to make them available in the project. To Do that, right-click on the project in Solution Explorer and select "Manage Imported Projects". Bring over all of the projects and you can now see them in Object Explorer (when you have an automation open).