Although more computationally demanding, several quantum chemistry programs considering multi-configuration electron correlation based on spin-dependent molecular orbitals have also been developed. For instance, in the relativistic software package DIRAC, multiconfigurational self-consistent field theory (MCSCF), generalized active space configuration interaction (GASCI), and Fock-space coupled-cluster singles and doubles (FSCCSD) are integrated. Density Matrix Renormalization Group (DMRG) calculations can be performed using the QCMaquis program by combining with the relativistic molecular orbital integrals created by the DIRAC software. Additionally, the software BAGEL enables various multiconfigurational calculations, such as MCSCF, complete active space second-order perturbation theory (CASPT2), n-electron valence state second-order perturbation theory (NEVPT2), and internally contracted MRCI including Davidson correction (ic-MRCI+Q), based on the four-component Hamiltonian. The Chronus Quantum software package provides MRCI and MRPT2 calculations using the exact two-component (X2C) relativistic Hamiltonian. Calculations using these programs generally incur high computational costs, and their application to moderate-sized molecules involving actinide atoms would pose a significant challenge for these methodologies.