XmCommandSetValue(3) on Linux
The text f8afb706ddfd, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
A Command function that replaces a displayed string "XmCommandSetValue" "Command functions" "XmCommandSetValue"