Man pages matching name xmvacreateseparatorgadget in section 3:

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