Man pages matching name xmvacreatemanagedpushbuttongadget in section 3:

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