FYI,
Attached is a document that lists all the bug fixes and enhancements (submitted via Esri Technical Support) that were addressed in Web AppBuilder for ArcGIS Developer Edition v2.6. Please be aware that the list may include items that were found in the embedded version of Web AppBuilder in ArcGIS Online and Portal for ArcGIS.
Hope this helps,
Derek,
What's the preferred mechanism to submit Web AppBuilder enhancements?
esri tech support or the Ideas place on GeoNet