Learning and working tasks in vocational education and training (VET) in the field of mechanical engineering comprise theoretical knowledge and practical activities, for instance, manufacturing a workpiece using a CNC turning machine. To clarify the requirements of these extensive tasks and the support by a mobile application, trainers of companies with training facilities were interviewed. The results of a qualitative content analysis with regard to application and task areas, communication patterns, learning materials, and expectations towards mobile learning are described in this article. Additionally, the resulting practical experiences and the expectations of trainers are included in an instructional design for the support of formal learning and working tasks in VET.