What combination of OS X, Endnote, Word just WORKS?

Yes, I can confirm the EndNote X8.2 tools load for us in Word 2011 (version 14.7.7) on macOS 10.13.3. I have seen language related issues with Word being able to load the EndNote tools before. I’m going to do a test to emulate your language settings just to verify they work. In the meantime, I would suggest trying this simple test.

  1. Quit Word.
  2. In EndNote, click the EndNote menu and select Customizer.
  3. De-select the Cite While You Write Component and click Next through the screens.
  4. When that is done, click the EndNote menu again and select Customizer.
  5. Select the Cite While You Write Component and click Next through the screens.
  6. Start Word and see if the correct items are now loading under Templates and Add-ins. If they are, you should be able to click OK and see the EndNote X8 sub-menu under the Tools menu.

If the issue persists, I would test with a new user account:

https://support.apple.com/kb/PH25796