Add N&N entry for changes in enhanced and custom folding regions

Contributes to eclipse-jdt/eclipse.jdt.ui#2860

Author: fedejeanne

news/4.40/jdt.md

@@ -16,7 +16,30 @@ A special thanks to everyone who [contributed to JDT](acknowledgements.md#java-d
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 ## Java Editor
 -->
+## Java Editor
+
+### Improvements for Enhanced Folding and Custom Folding Regions
+<details>
+<summary>Contributors</summary>
+
+- [Federico Jeanne](https://github.com/fedejeanne)
+- [Daniel Schmid](https://github.com/danthe1st)
+</details>
+
+
+#### Visible Improvements
+
+Several improvements have been made to the enhanced folding and the custom folding regions features introduced in previous releases, including:
+- The performance of the enhanced folding mechanism has been improved, especially for large files with many foldable elements.
+- Folding regions now include the entire body of control statements, including the opening and closing braces, for a more intuitive folding experience.
+- Minor glitches in the folding behavior have been fixed.
+- The complete list of addressed issues can be found in the following PR: https://github.com/eclipse-jdt/eclipse.jdt.ui/pull/2860
+
+#### API/Contract clarifications
 
+With these changes, custom subclasses of `DefaultJavaFoldingStructureProvider` will also contain the enhanced and the custom folding regions in their results
+if the appropriate preferences have been activated.
+If this is not desired by the subclass, the regions will have to be explicitly removed from the result.
 <!--
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 ## Java Views and Dialogs