We analyze the subleading three-nucleon contact interaction terms at N4LO in chiral effective field theory. We perform the isospin projection into $T=1/2$ and $T=3/2$ states, and find that only eleven of the thirteen operators contribute in the $T=1/2$ channel. By projection on the partial waves of the asymptotic configuration of $N-d$ scattering states in momentum space, we find contributions from ten combinations of LECs. These results provide a useful basis for including N4LO three-body forces in few-body calculations and for constraining them through numerical fits to data.