Incorporate review (jreback); add subsection header [ci skip]

Author: h-vetinari

doc/source/whatsnew/v0.24.0.txt

@@ -8,6 +8,13 @@ v0.24.0 (Month XX, 2018)
 New features
 ~~~~~~~~~~~~
 
+.. _whatsnew_0240.enhancements.excel_writer_mode:
+
+``mode`` for ``ExcelWriter``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+``ExcelWriter`` now accepts ``mode`` as a keyword argument, enabling append to existing workbooks when using the ``openpyxl`` engine (:issue:`3441`)
+
 .. _whatsnew_0240.enhancements.extension_array_operators:
 
 ``ExtensionArray`` operator support
@@ -68,7 +75,6 @@ Current Behavior:
 
 Other Enhancements
 ^^^^^^^^^^^^^^^^^^
-- ``ExcelWriter`` now accepts ``mode`` as a keyword argument, enabling append to existing workbooks when using the ``openpyxl`` engine (:issue:`3441`)
 - :func:`to_datetime` now supports the ``%Z`` and ``%z`` directive when passed into ``format`` (:issue:`13486`)
 - :func:`Series.mode` and :func:`DataFrame.mode` now support the ``dropna`` parameter which can be used to specify whether NaN/NaT values should be considered (:issue:`17534`)
 - :func:`to_csv` now supports ``compression`` keyword when a file handle is passed. (:issue:`21227`)