Man pages matching name xmvacreatemanagedspinbox in section 3:

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