We identify two types of well-motivated, so-far experimentally unexplored LHC signatures of extended Higgs sectors: First, Higgs-to-Higgs decay signatures that involve (at least) two Beyond-the-Standard Model (BSM) neutral scalar bosons, $\phi_i \to \phi_j \phi_k$. These signatures are discussed in the framework of the Two-Real-Singlet-Model (TRSM), which can furthermore exhibit cascades of Higgs-to-Higgs decays leading to multi-Higgs final states. Second, the charged Higgs boson decay to a $W$ boson and a neutral BSM Higgs boson, which can easily become the dominant decay within the Two-Higgs-Doublet-Model (2HDM) parameter space. We provide benchmark scenarios for future experimental studies of these signatures.