The rise of behavior trees (BTs) as a versatile tool for modeling complex, hierarchical behaviors has created a need for intuitive and effective graphical user interfaces (GUIs) to manage and interact with these structures. This thesis presents the design, development, and evaluation of a custom GUI tailored for BT management, specifically aimed at applications in industrial robotics, smart home automation, healthcare monitoring, and autonomous systems. The user-friendly GUI developed with PyQt5 enables users to easily create, visualize, and simulate BTs. It includes convenient features such as drag-and-drop functionality for creating nodes, dynamic properties dialogs for nodes, context menus for efficient node management, and real-time simulation capabilities. By integrating PyTrees, a Python-based BT library, the GUI seamlessly translates visual BTs into executable structures, allowing users to validate their designs through simulations interactively. The usability of the GUI was evaluated using the System Usability Scale (SUS)and qualitative feedback from a diverse group of participants, including professionals from ABB and university students. The results indicated a high level of user satisfaction, with an average SUS score well above industry benchmarks. While recommendations for more customization choices and improved search capabilities were offered, participants appreciated the system’s straightforward design and simplicity of use. This thesis contributes to the field of GUI design and BTs by offering a versatile tool that bridges the gap between conceptual BT design and practical implementation. The findings emphasize the importance of user-centered design in developing effective software tools and highlight potential avenues for future enhancements, including broader domain applications and integration with advanced technologies likelarge language models like ChatGPT.