From the announcement:
The new version is a greatly enhancing the usability of KNIME. It adds new features like workflow annotations, support for hotkeys, inclusion of R-views in reports, data flow switches, option to hide node labels, variable support in the database reader/connector and R-nodes, and the ability to export KNIME workflows as SVG Graphics.
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With the 2.3 release we are also introducing a community node repository, which includes KNIME extensions for bio- and chemoinformatics and an advanced R-scripting environment.