The objective of this design case was to describe the development of an online graph-oriented tool to support the representation of collaborative argumentation for middle school students from a faculty expert's perspective and discuss the processes that were instrumental in developing the tool. Supported by the professional staff in the Digital Convergence Lab (DCL) at Northern Illinois University, a student team was involved in the development process of such a tool. Based on the design document from the design team, the development team developed a prototype and the faculty expert conducted a series of usability tests with 119 middle school students in the United States. Overall, the results of the usability testing suggested that the prototype is targeted at supporting the representation of scientific argumentation. The student participants also provided suggestions for further improvement of the prototype.