By default, the categories that are specified using the [wiki-links] or the [[squarebrackets]] syntax do not appear in the graph, but in the top Filter menu (top left under the "Filter: All the Statements tab).
If you want to change that default behavior and to have the categories also be added into the graph, you need to set this in the settings panel:
1) Go to the Settings http://infranodus.com/settings
2) Choose (Graph) Editor
3) Go to >> Words inside [Squarebrackets] and [[Squarebrackets]] will be >> Recorded as Tags / Categories and Added into the graph (3rd option).
This way your [wiki-links] will be recorded as tags (and available under the filter menu) and also added into the graph (so you can also add phrases this way).