With respect, it is a project name not a menu. You can see in your screen shot the name of the project, "Color Filters and Gradients", at the top middle of the screen. Under the Project Media heading at the top of the sidebar is displayed the name of the project, "Color Filters and Gradients", and when selected as shown in your screen shot, the project name "Color Filters and Gradients" will be displayed in the bar above the browser.
You screen shot is of an iMovie 10 project. I can assure you that in no other previous versions of iMovie 10 was there ever a
Color Filters and Gradients menu item.
-- Rich