XmCreateCascadeButton(3) on Linux
The text 52508d4581c3, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
The CascadeButton widget creation function "XmCreateCascadeButton" "creation functions" "XmCreateCascadeButton"