XmScaleSetValue(3) on Linux
The text 5cd645acb00d, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
A Scale function that sets a slider value "XmScaleSetValue" "Scale functions" "XmScaleSetValue"