Man pages matching name xmvacreatemanagedfileselectionbox in section 3:

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