Hi,
I you are trying to customize the contents of a shortcut menu (i.e., context menu). This feature is not available in Autodesk Inventor, though here are some alternatives like you can use the Alt+Ctrl+H keyboard shortcut to trigger the Replace All command or you would be able to map the keypress to a button on your mouse or motion controller, giving you one-click access to the command and you can also drag and drop the Replace All command from the Customize dialog to a toolbar or the Panel Bar and execute it from there.
Enjoy!