Man pages matching name xmvacreatemanageddropdown in section 3:

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