  The helical magnetic structures of cubic chiral systems are well-explained by
the competition among Heisenberg exchange, Dzyaloshinskii-Moriya interaction,
cubic anisotropy, and anisotropic exchange interaction (AEI). Recently, the
role of the latter has been argued theoretically to be crucial for the
low-temperature phase diagram of the cubic chiral magnet Cu$_2$OSeO$_3$, which
features tilted conical and disordered skyrmion states for a specific
orientation of the applied magnetic field ($\mu_0 \vec{\mathrm{H}} \parallel
[001]$). In this study, we exploit transmission resonant x-ray scattering
($t-$REXS) in vector magnetic fields to directly quantify the strength of the
AEI in Cu$_2$OSeO$_3$, and measure its temperature dependence. We find that the
AEI continuously increases below 50\,K, resulting in a conical spiral pitch
variation of $10\%$ in the (001) plane. Our results contribute to establishing
the interaction space that supports tilted cone and low-temperature skyrmion
state formation, facilitating the goals for both a quantitative description and
eventual design of the diverse spiral states existing amongst chiral magnets.
