  Recent improvements in the sensitivity and precision of the radial velocity
(RV) method for exoplanets have brought it close, but not quite to, the
threshold ($\sim$10 cm/s) required to detect Earth-mass and other potentially
habitable planets around Sun-like stars. Stellar activity-driven noise in RV
measurements remains a significant hurdle to achieving this goal. While various
efforts have been made to disentangle this noise from real planetary signals, a
greater understanding of the relationship between spectra and stellar activity
is crucial to informing stellar activity mitigation. We use a partially
automated method to analyze spectral lines in a set of observations of the
young, active star $\epsilon$ Eridani from the high-precision spectrograph
NEID, correlate their features (depth, full width at half maximum, and
integrated flux) with known activity indicators, and filter and curate for
well-behaved lines whose shape changes are sensitive to certain types of
stellar activity. We then present a list of 9 lines correlated with the S-index
in all three line features, including 4 newly-identified activity-sensitive
lines; as well as additional lines correlated with S-index in at least one
feature, and discuss the possible implications of the behavior observed in
these lines. Our line lists represent a step forward in the empirical
understanding of the complex relationships between stellar activity and
spectra, and illustrate the importance of studying the time evolution of line
morphologies with stabilized spectrographs, in the overall effort to mitigate
activity in the search for small, potentially Earth-like exoplanets.
