In a world where activities, goals and available software are rapidly changing, users must constantly adapt. In this position paper, we discuss how digital skills are different from traditional skills due to their highly dynamic na-ture, both in the tools used and the tasks to be carried out. We advocate the needs both for interdisciplinary theory to conceptualize digital skill develop-ment, and for longitudinal, large-scale and trace-based methods to observe such phenomenon. We illustrate how digital tools could better support users in the development of skills, highlighting how traces of interaction could be leveraged within reflective and skill-sharing tools.