The positronium atom, a bound state of electron and positron, is a suitable leptonic test site for Charge-Parity (CP) discrete symmetry research. According to the Standard Model, the photon–photon interaction in the final state due to the vacuum polarization may mimic CP violation of the order of 10, while weak interaction effects lead to a violation of the order of 10. So far, the experimental limits on CP symmetry violation in the decay of o-Ps are set at the level of 10. The J-PET detector can be used to explore discrete symmetries by looking for probable non-zero expectation values of the symmetry-odd operators, constructed from spin of ortho-Positronium (o-Ps) and momentum, and polarization vectors of gamma (γ) quanta resulting from o-Ps annihilation. The upgraded version of the J-PET detector, with an additional fourth layer of detection modules increases signal acceptance, which allows to triple the efficiency of γ quanta detection for CP discrete symmetry studies.