Business process models help to visualize processes of an organization. In enterprises, these processes are often specified in internal regulations, resolutions or other law acts of a company. Such descriptions, like task lists, have mostly form of enumerated lists or spreadsheets. In this paper, we present a mapping of process model elements into a spreadsheet representation. As a process model can be represented in various notations, this can be seen as an interoperability solution for process knowledge interchange between different representations. In presenting the details of the solution, we focus on the popular BPMN representation, which is a de facto standard for business process modeling. We present a method how to generate a BPMN process model from a spreadsheet-based representation. In contrast to the other existing approaches concerning spreadsheets, our method does not require explicit specification of gateways in the spreadsheet, but it takes advantage of nested list form. Such a spreadsheet can be created either manually or merged from the task list specifications provided by users.