The paradigm shift triggered by Industry 4.0 leads to a fast rising number of industrial machinery and collaborative robots that increases the need for flexible customization of production processes and automation workflows. End-user programming of industrial robots has become an essential capability for all areas in industry. Consequently, different visual programming languages have found their way into the domain of industrial robot programming. In this paper, we investigate the applicability of block-based programming languages for large and complex robot programs in realistic environments. Here, a key aspect of robot programming is not only the interaction with the physical environment, but also the robot’s interaction with other shopfloor participants at the software control level. To this end, we analysed the requirements for programming a robot based a real world production cell and implemented the necessary programming constructs using Blockly, an open-source block-based visual language. We assessed the results comparing the implementation of a change in Blockly and the Sequential Function Chart-based language. We find that while Blockly is able to express large and complex real-world robot programs, a major contributing factor is not just the language itself but the presentation of the robot’s run-time environment as well as support by the development environment (i.e., editor). Our preliminary user experiment has identified a set of challenges in understanding and changing such programs that we now plan to follow-up with a larger user study.