We investigated the low-temperature helical magnetic structures in a thin plate of chiral magnet FeGe, paying special attention to the variation of the magnetic modulation period with the angle of an applied magnetic field. A unique vector-field setup allowed us to continuously rotate the helical texture in the sample plane while measuring high-resolution resonant small-angle x-ray scattering patterns. The experiments and supporting micromagnetic simulations show that the direction of helical propagation can be robustly controlled by directional magnetic field training. The observed anisotropy of the helical modulation period is explained naturally by inclusion of higher-order anisotropic exchange in the Bak-Jensen model. The observation and estimation of this interaction provides a pathway to refine theoretical models of cubic chiral magnets and design spintronics devices based on the propagation switching of helical textures.