In order to customize the Dynamics 365 ribbon, you can either edit the XML manually or you can use a ribbon editing tool. Microsoft MVP Scott Durow has done such a good job implementing his Ribbon Workbench that I seldom use anything else to edit Dynamics 365 ribbons. In order to get the Ribbon Workbench, you can either get it as part of the Microsoft MVP Tanguy Touzard's XrmToolBox, or you can download the managed solution from https://www.develop1.net/public/rwb/ribbonworkbench.aspx. A System Customizer or higher role is required to edit the ribbon XML.