XmTextInsert(3) on Linux
The text c62afd4c2187, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
A Text function that inserts a character string into a text string "XmTextInsert" "Text functions" "XmTextInsert"