Need superscript, subscript, and strikethrough at the ready? Great! You can add these buttons to the Quick Access Toolbar. Just go to Excel > Preferences > Ribbon & Toolbar. Once you're there, click the Quick Access Toolbar tab. Then, under Choose commands from, choose All Commands. Finally, select either the Superscript, Subscript, or Strikethrough button and then click the > button to move it over.
Want to customize Excel even more? You can read all about that here.
