Man pages matching name xmvacreatecascadebuttongadget in section 3:

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