Dark matter (DM) in the Milky Way may annihilate or decay directly into gamma rays, producing a monoenergetic line-like excess in the energy spectra. If detected, such features would provide a clear DM signature. In this work, we present an update on line search with 13.75 years of Fermi Large Area Telescope (LAT) data from 1 GeV to 1 TeV in five sky regions centered on the Galactic Center, optimized for different DM density profiles and annihilation or decay channels. We improve the fitting procedure by combining the likelihood profiles for different energy dispersion event types (EDISP). To account for systematic uncertainties, we include the data from the control region along the Galactic plane in the fit procedure. We find no statistically significant evidence of features in our data, and set constraints on the velocity-averaged DM annihilation cross sections and on the DM decay time. Compared to the previous Fermi-LAT results, the limits on the DM parameters at 95\% confidence level in the low energy band are even stronger up to 1-2 orders of magnitude depending on the sky region, thanks to the improved analysis method.