How can I modify the Windows 10 Explorer Ribbon?
Solution 1:
I am pretty sure (greater than 90%) that you cannot change the Windows Explorer ribbon.
It is used as an underpinning for file operations by many applications (Office and more) and so is fixed in its nature.
Solution 2:
@John is correct that file explorer ribbon items cannot be changed or new items cannot be created.
Instead you can create context menus (the menus which appear when you right click files/folders or objects in Windows shell and file system). You can explore file association and shell/context menu keys at HKEY_CLASSES_ROOT.