Man pages matching name xmvacreatepushbuttongadget in section 3:

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