This feature contains several node for reading, manipulating,
and writing XML data.
Extension 
KNIME JSON-Processing
Included nodes & related workflows
Legal
Copyright by KNIME AG, Zurich, Switzerland
Update site information
KNIME Analytics Platform 4.4 Update Site, Version 4.4.0
http://update.knime.com/analytics-platform/4.4
In case you can’t install the extension via drag & drop, please check that the update site is activated.