Multiparticle correlations built from azimuthal angles whose distributions have been parametrized with the Fourier series expansion, depend generically on two distinct degrees of freedom: flow amplitudes $v_n$ and symmetry-planes $\Psi_n$. While analyses techniques for flow amplitudes $v_n$ have advanced over the past years, robust and unbiased techniques for analysing symmetry-planes $\Psi_n$ still need to be developed. Previous attempts in the measurements of symmetry-plane correlations (SPC) in high-energy nuclear collisions have built-in biases due to neglected correlations between the flow amplitudes $v_n$ themselves. In this poster, we summarize the recent improvements in the direction of newly developed analyses techniques for SPC without these built-in biases. Predictions of these new observables in high-energy nuclear collisions are provided for the initial coordinate space by MC-Glauber and for the momentum space by iEBE-VISHNU.