Man pages matching name xmvacreatemanagedpanedwindow in section 3:

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