refer to #18 in release notes

docs/releases.rst

@@ -17,7 +17,8 @@ Breaking changes
   (:issue:`336`, :pull:`338`) By `Tom Nicholas <https://github.com/TomNicholas>`_.
 - Indexes are now created by default for any loadable one-dimensional coordinate variables. 
   Also a warning is no longer thrown when ``indexes=None`` is passed to ``open_virtual_dataset``, and the recommendations in the docs updated to match.
-  (:pull:`357`) By `Tom Nicholas <https://github.com/TomNicholas>`_.
+  This also means that ``xarray.combine_by_coords`` will now work when the necessary dimension coordinates are specified in ``loadable_variables``.
+  (:issue:`18`, :pull:`357`) By `Tom Nicholas <https://github.com/TomNicholas>`_.
 
 Deprecations
 ~~~~~~~~~~~~