Built-in Control Scanner
You use Built-in Controls Scanner to find command bar names and built-in controls IDs.
Office provides a common term for toolbars, menus and context menus. This term is command bar. Command bars are distinguished by their names while command bar controls are distinguished by their IDs. Custom command bar controls can be placed before or after a given built-in control. For instance, you may want to place your custom button before the Save button. To achieve this, you use the Built-in Control Scanner to find the ID of the Save button. Then you use this ID in the code that adds your control. Note that in Add-in Express command bar control components, you would just specify the ID of the Save button in the BeforeIdMso property of your control.
How to find a command bar associated with a context menu