  A vortex in an s-wave superconductor with a surface Dirac cone can trap a
Majorana bound state with zero energy leading to a zero-bias peak (ZBP) of
tunneling conductance. The iron-based superconductor FeTe$_x$Se$_{1-x}$ is one
of the material candidates hosting these Majorana vortex modes. It has been
observed by recent scanning tunneling spectroscopy measurement that the
fraction of vortex cores possessing ZBPs decreases with increasing magnetic
field on the surface of this iron-based superconductor. We construct a
three-dimensional tight-binding model simulating the physics of over a hundred
Majorana vortex modes in FeTe$_x$Se$_{1-x}$ with realistic physical parameters.
Our simulation shows that the Majorana hybridization and disordered vortex
distribution can explain the decreasing fraction of the ZBPs observed in the
experiment. Furthermore, we find the statistics of the energy peaks off zero
energy in our simulation with the Majorana physics in agreement with the
analyzed peak statistics in the vortex cores from the experiment. This
agreement and the explanation of the decreasing ZBP fraction lead to an
important indication of scalable Majorana vortex modes in the iron-based
superconductor. Thus, FeTe$_x$Se$_{1-x}$ can be one promising platform
possessing scalable Majorana qubits for quantum computing. In addition, we
further show the interplay of the ZBP presence and the vortex locations
qualitatively agrees with our additional experimental observation and predict
the universal spin signature of the hybridized multiple Majorana vortex modes.
