How do I format my Add Item dropdown list

I started to create my own template. Is there a way to add options to my Add Item dropdown menu? I cannot seem to find anywhere to do that.

Have a look at the interactive tutorial, in the Help menu, in the yellow “Going Further” section, under “Customising Projects”, and “Document Templates”. That section will walk you through setting up a document template folder in the binder, and show how you can create entries which will populate the “Add” button, as well as the Project ▸ New from Template submenu.

You might want to just have this open alongside your project, and follow the steps it describes there, instead of doing it twice.