Robot programming for complex assembly tasks is challenging and demands expert knowledge. With Augmented Reality (AR), immersive 3D visualization can be placed in the robot's intrinsic coordinate system to support robot programming. However, AR interfaces introduce usability challenges. To address these, we introduce a hybrid user interface (HUI) that combines a 2D desktop, a smartphone, and an AR head-mounted display (HMD) application, enabling operators to choose the most suitable device for each sub-task. The evaluation with an expert user study shows that an HUI can enhance efficiency and user experience by selecting the appropriate device for each sub-task. Generally, the HMD is preferred for tasks involving 3D content, the desktop for creating the program structure and parametrization, and the smartphone for mobile parametrization. However, the device selection depends on individual user characteristics and their familiarity with the devices.

Skill-based programming has proven to be advantageous for assembly tasks, but still requires expert knowledge, especially for force-controlled applications. However, it is error-prone due to the multitude of parameters, e.g. different coordinate frames and either position-, velocity- or force-controlled motions on the axes of a frame. We propose a mixed reality based solution, which systematically visualizes the geometric constraints of advanced high-level skills directly in the real-world robotic environment and provides a user interface to create applications efficiently and safely in mixed reality. Therefore, state-machine information is also visualized, and a holographic digital twin allows the user to ad-hoc validate the program via force-enabled simulation. The approach is evaluated on a top hat rail mounting task, proving the capability of the system to handle advanced assembly programming tasks efficiently and tangibly.