The advent of advanced technology has opened new horizons for studying collaborative learning, although ambiguity remains in the classification and rationale for combining modalities in multimodal collaboration analytics (MMCA). Addressing this gap is crucial for the progression of collaborative learning practices and research. This review critically examines and classifies the modalities employed in MMCA studies while elucidating the rationales for their combined use and their resulting empirical contributions to collaborative learning research. A scoping review of 36 empirical studies informs the development of a framework for classifying modalities used in MMCA. We also review the rationales underlying the use of different combinations of modalities and how MMCA literature contributes to our understanding of collaboration. The review results in a definitional framework comprising five categories: auditory, visual, physiological, kinesthetic, and tactile. The findings reveal diverse arrangements of modalities. We find that the underlying rationales for combining modalities are based on technical, practical/pedagogical, methodological, or theoretical premises, which lead to different empirical contributions. Conducting MMCA research is motivated by the need for a holistic comprehension of learner behaviours, interactions, and cognitive processes during collaboration, transcending the limitations of single modalities in isolation. These findings offer both a theoretical and practical guidepost for enhancing MMCA research and applications.