You can keybind keys via the bind command options, this may be important.
Bind keys to up and down for your menu as well as use and escape, and create scripts that if those keys are pressed, you're navigating a variable up or down or choosing an item, or escaping the menu
Create images that go on screen, dending on where those two variables are, These will be your cursors.
Then for each inventory item you have, you'll create a place on the screen to store that image, and a script that goes with it. So. when you scroll to each item, and then hit enter. It will 'USE' that menu item. Of course, Easy FPS Editor IS limited by what you can DO with that. But.... have fun?