SignificanceMicroscale collectives composed of simple, locally reactive constituents can harness the effects of self-organization to enable diverse global behaviors. While phase separation of homogeneous collectives is well studied, heterogeneous collectives are relatively unexplored. This study focuses on a collective of magnetic microdisks of different sizes and examines how the group can self-organize into homogeneous subgroups using an external magnetic field. We find that heterogeneity enables collective behaviors including morphology reconfiguration, organized aggregation, dispersion, and locomotion, and caging and expulsion of external objects. Our work furthers insights into self-organization of heterogeneous microrobot collectives and may provide useful insights into the future of active matter.