Man pages matching name xmcreatecascadebuttongadget in section 3:

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