Added whatsnew note in Bug Fixes / Reshaping

Author: Kristian Holsheimer

doc/source/whatsnew/v0.24.0.txt

@@ -883,6 +883,7 @@ Reshaping
 - Bug in :func:`pandas.wide_to_long` when a string is passed to the stubnames argument and a column name is a substring of that stubname (:issue:`22468`)
 - Bug in :func:`merge` when merging ``datetime64[ns, tz]`` data that contained a DST transition (:issue:`18885`)
 - Bug in :func:`merge_asof` when merging on float values within defined tolerance (:issue:`22981`)
+- Fixed :meth:`DataFrame.nsmallest` and :meth:`DataFrame.nsmallest` for dataframes that have :class:`MultiIndex`ed columns (:issue:`23033`).
 
 Build Changes
 ^^^^^^^^^^^^^