During the past decades, weakly coupled spin cluster systems have attracted much attention due to the possibility of observing concomitantly zero-dimensional quantum and three-dimensional collective magnetism. In such systems, there is an energy hierarchy of low-lying magnetic excitations between transverse and longitudinal magnon modes and localized excitations. The recently discovered hexagonal perovskite Ba4NbMn3O12 provides an ideal platform to address a crossover of molecular magnetism to collective behavior as its magnetic building block is Mn3O12 trimers. Ba4NbMn3O12 exhibits a long-range magnetic ordering at Tc=42K with a small value of Curie-Weiss temperature Tcw=-4K. In this project, we aim at comprehensive muSR studies to elucidate a multistage symmetry breaking process arising from the energy hierarchy of exchange interactions in the coupled spin trimer compound Ba4NbMn3O12.