Man pages matching name xmdropsiteconfigurestackingorder in section 3:

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