I am really new to Concordion. I just want to know if cross-feature testing, cause-effect graphing, scenario testing and usability testing are available in Concordion. I have searched everywhere but seemed to find nothing.
You can use the concordion:run command to execute active specifications from another one. This helps you to implement cross-feature testing with Concordion. You can use a SVG tool to create a cause-effect graph, if you would like to include the graph into your Concordion specifications. Moreover, Concordion allows applying the concordion:execute command on tables. Thus, you can represent the test matrix from your cause-effect graphing in Concordion for automated testing. With Concordion you can define tests of arbitrary complexity. Thus, you can create test cases with simple steps or more complex scenarios covering many steps. Usability testing is based on user interaction to evaluate a product. If you want to make detailed analysis and reporting, you would probably use a statistics tool rather than a test tool.
The techniques you are asking for where developed with manual testing in mind. They can in some way be applied to automated testing as well. Concordion is a tool that is well suited for behavior driven development (bdd) and specification by example (sbe) where the goal is to develop a common understanding with the team and different stakeholders. For inspiration see for example the following key note: http://vimeo.com/109079233