There has been a growing recognition that a systems thinking approach, which pays attention to the entire dynamic system, its constituent parts and the interactions among those parts, is an effective approach for tackling complex issues that exhibit nonlinear behaviour and involve multiple stakeholders. To understand a complex system, a systems thinking approach must identify the leverage points, which are non-intuitive and difficult to identify. This paper proposes a design tool called System Design Canvas, which supports the identification of system variables and leverage points from technological sensing data and human data while understanding stakeholders' mental model. The present case study confirms that System Design Canvas can identify system variables and leverage points that are required for the current agricultural system in Cambodia.