  We investigate the magnetic-field dependent evolution of the zero-bias
conductance peaks (ZBCPs) on the nanoscale bismuth islands grown on the
FeTe$_{0.55}$Se$_{0.45}$ substrate. The ZBCPs can be observed throughout the
entire region on these islands, and their characteristics align with the
signatures of Majorana zero modes. Remarkably, the evolution of ZBCPs on these
islands exhibits anomalous behavior under varying magnetic fields: The
magnitude of ZBCPs is first enhanced at weak fields lower than 2 T and then
suppressed as the fields further increase. We attribute the non-monotonic
evolution of the ZBCPs to the magnetic-field-enhanced topological edge states
on these Bi islands. Our findings provide valuable insights into the probable
origin of the Majorana zero modes in the Bi-island platform and the
magnetic-field response of topological edge states.
