Man pages matching name xmcascadebuttongadgethighlight in section 3:

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