In earlier versions of TPT, there was a "secret" keyboard shortcut to get to a secret menu that had the "secret" elements. That's been removed since...a really long time ago (v46.4, I think).
Looking through powder.h in the source, I can see MORT, RIME, FOG, LOVE, FRZW, BIZG, BIZS, EQVE, SHD2, SHD3, SHD4, LOLZ, and PSTS that are part of the SC_CRACKER or SC_CRACKER2 menus (those menus are never displayed in game).
Of course, you can actually create RIME, FOG, FRZW, BIZG, BIZS, SHD2, SHD3, SHD4, and PSTS using elements that are not "secret"....