New results on inclusive jets, dijet and trijet differential cross sections in neutral-current deep-inelastic $ep$ scattering (DIS) using the H1 detector at HERA are presented. The DIS phase space of this measurement is given by the virtuality of the exchanged boson $5 < Q^2 <100$ GeV$^2$ and the inelasticity of the interaction $0.2<y<0.65$. Jets are defined in the Breit frame using the $k_T$ jet-algorithm and are required to be in the pseudorapidity range in the laboratory rest frame of $-1.0<\eta_{\rm lab}<2.5$. The transverse momentum of the jets is required to exceed $P_T^{\text{jet}}>5$ GeV. Differential cross sections are measured as a function of $Q^2$ and $P_T^{\text{jet}}$ for inclusive jets, and for dijet and trijet events as a function of $Q^2$ and the average transverse momentum of the two jets with the highest transverse momentum in an event, $\langle P_T \rangle$. The data are compared to predictions in next-to-leading order perturbative QCD and and overall reasonable agreement within the sizeable uncertainties of the predictions is found. The new data complement a previous H1 measurement at higher momentum transfer $Q^2 >150$ GeV$^2$.