This study aims to inform the design of mobile apps for vocabulary learning. Learning vocabulary involves developing, connecting, and sustaining various types of knowledge and skills. Learners do not typically acquire these all at once, but rather over the course of distinct episodes of activity. Yet, little is known about learning experience designs that help learners connect these episodes, which often make use of different socio-technical resources, and are distributed over time, and across settings. We use participatory design to explore how mobile apps might help learners enact episodes of learning activity and connect these in effective vocabulary learning trajectories. In order to stimulate design thinking, six adult language learners used an app for self-directed vocabulary learning in authentic conditions for from six weeks to six months. Then, in a post-study workshop, participants developed new designs for scaffolding self-directed vocabulary learning trajectories, grounded in reflection on their own experiences. [For full proceedings, see ED565087.]