  Particle tracks and differential energy loss measured in high pressure
gaseous detectors can be exploited for event identification in neutrinoless
double beta decay~($0\nu \beta \beta$) searches. We develop a new method based
on Kalman Filter in a Bayesian formalism (KFB) to reconstruct meandering tracks
of MeV-scale electrons. With simulation data, we compare the signal and
background discrimination power of the KFB method assuming different detector
granularities and energy resolutions. Typical background from $^{232}$Th and
$^{238}$U decay chains can be suppressed by another order of magnitude than
that in published literatures, approaching the background-free regime. For the
proposed PandaX-III experiment, the $0\nu \beta \beta$ search half-life
sensitivity at the 90\% confidence level would reach $2.7 \times 10^{26}$~yr
with 5-year live time, a factor of 2.7 improvement over the initial design
target.
