Excel: Customize Ribbon Feature

You can customize the Excel Ribbon by creating your own tabs with whichever commands you want. Commands are always housed within a group, and you can create as many groups as you want in order to keep your tab organized. If you want, you can even add commands to any of the default tabs, as long as you create a custom group in the tab. You also can change the view of quick access toolbar too. Personalize your ribbon to arrange tabs and commands in the order you want them, hide or unhide your ribbon, and hide those commands you use less often. Although you can't share customizations between apps, you can export your customizations to share with others or use on other devices. Customizations apply only to the Office program you're working in at the time. For example, if you personalize your ribbon in MS Word, those same changes won't be visible in Excel. If you want similar customizations in your other Office apps, you'll have to open each of those apps to make the same changes.

You cannot reduce the size of your ribbon, or the size of the text or the icons on the ribbon. The only way to do this is to change your display resolution, which would change the size of everything on your page. If the ribbon is not visible at all then you probably have the state set to full screen mode. Select More at the top right of the screen. This will temporarily restore the ribbon.