  Moir\'e excitons are emergent optical excitations in 2D semiconductors with
deep moir\'e superlattice potentials. While these excitations have been
realized in several platforms, a system with dynamically tunable moir\'e
potential to tailor the moir\'e exciton properties is yet to be realized. Here,
we present a continuously tunable moir\'e potential in a monolayer WSe2 that is
enabled by its proximity to twisted bilayer graphene (TBG) near the
magic-angle. Due to its flat electronic bands, charge distribution is highly
localized and forms a triangular lattice in TBG. Tuning the local charge
density via electrostatic gating, TBG thus provides a spatially varying and
dynamically tunable dielectric superlattice for modulating monolayer exciton
wavefunctions. By performing optical reflection spectroscopy, we observe
emergent moir\'e exciton Rydberg branches in monolayer WSe2 with increased
energy splitting upon doping TBG. The twist-angle dependence reveals that the
observation is due to a hybridization between bright and dark Rydberg states
enabled by the moir\'e potential. Further, at the magic-angle near 1.1{\deg},
the moir\'e Rydberg excitons form a sawtooth pattern with doping owing to the
formation of strongly correlated states in the TBG. Our study provides a new
platform for engineering moir\'e excitons as well as optical accessibility to
the electronic states with small correlation gaps in TBG.
