Man pages matching name xmvacreatemanagedcascadebuttongadget in section 3:

XmVaCreateManagedCascadeButtonGadget.3.en	debian 10 / libmotif-dev
XmVaCreateManagedCascadeButtonGadget.3.en	debian 11 / libmotif-dev
XmVaCreateManagedCascadeButtonGadget.3.en	debian 12 / libmotif-dev