The history of dielectronic recombination (DR) is fill of, skepticism, hope, excitement, and finally, clear realization of its importance for hot high-Z plasmas. Using the NIST electron beam ion trap (EBIT), that is capable of reproducing conditions of future multi-million-Kelvin fusion reactors, we study dielectronic recombination in >50-times ionized heavy elements (such as tungsten) using highly forbidden low-energy magnetic-dipole lines. The newly proposed method allows for simultaneous in situ measurements of dielectronic resonances for several ions without "standard" beam ramping or ion extraction. Large-scale DR simulations show a strong effect of anisotropic unidirectional propagation of the electron beam on the plasma ionization balance.