bugfix was also needed in another place

ome_zarr/writer.py

@@ -251,6 +251,7 @@ def write_multiscale(
                 component=str(Path(group.path, str(path))),
                 storage_options=options,
                 compressor=options.get("compressor"),
+                dimension_separator=group._store._dimension_separator,
             )
         else:
             group.create_dataset(str(path), data=data, chunks=chunks_opt, **options)