Man pages matching name xmvacreatemanagedcascadebutton in section 3:

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