  We present a mock catalog of gravitationally lensed quasars at
$z_\text{qso}<7.5$ with simulated images for the Rubin Observatory Legacy
Survey of Space and Time (LSST). We adopt recent measurements of quasar
luminosity functions to model the quasar population, and use the CosmoDC2 mock
galaxy catalog to model the deflector galaxies, which successfully reproduces
the observed galaxy velocity dispersion functions up to $z_d\sim1.5$. The mock
catalog is highly complete for lensed quasars with Einstein radius
$\theta_E>0\farcs07$ and quasar absolute magnitude $M_{i}<-20$. We estimate
that there are $\sim10^3$ lensed quasars discoverable in current imaging
surveys, and LSST will increase this number to $\sim2.4\times10^3$. Most of the
lensed quasars have image separation $\Delta \theta>0\farcs5$, which will at
least be marginally resolved in LSST images with seeing of $\sim0\farcs7$.
There will be $\sim200$ quadruply-lensed quasars discoverable in the LSST. The
fraction of quad lenses among all discoverable lensed quasars is about
$\sim10\%-15\%$, and this fraction decreases with survey depth. This mock
catalog shows a large diversity in the observational features of lensed
quasars, in terms of lensing separation and quasar-to-deflector flux ratio. We
discuss possible strategies for a complete search of lensed quasars in the LSST
era.
