This menu includes the extra things that don’t have a home elsewhere.
This is a shortcut to the Excel add-ins menu. This is easier than going through the main menu and clicking several times.
If the current file is saved to a folder, this will open the folder in Windows Explorer. This good for finding a file if you have opened it from a link.
This opens a form that contains additional buttons. These are “developmental” features that are currently being tested. It is a non-trivial task to add buttons to the Ribbon, so it is only done once a feature is good and working. These buttons allow for running some additional code without having to open the VBA editor all the time. The features in here should be considered unstable and may not do what you think!