Digital multimodal composing (DMC) has become a central literacy practice in language education, yet research on teacher engagement remains conceptually fragmented and weakly linked to learner outcomes. This systematic review synthesises 51 empirical studies (2015–2025) that operationalise teacher engagement in DMC and examine its relationship with learner outcomes. Teacher engagement is organised into five interrelated dimensions: Orientation, Knowledge, Design, Assessment, and Enactment (OK-DAE), functioning as an analytic heuristic for mapping the literature. Using descriptive and co-occurrence analyses, alongside R (v. 4.5.1) for data visualisation and quantitative mapping, results show that Design and Enactment dominate the evidence base, while Orientation and Assessment are under-examined, and Knowledge is rarely examined. Moreover, only two studies report statistically tested learner outcomes alongside explicit teacher-engagement evidence. The findings reveal a persistent “last-mile” gap between pedagogical engagement and measurable learning progress, highlighting the need to strengthen how teacher engagement is conceptualised, measured, and supported.