gtk:combo-box-text-append (combo id text)

combo -- a gtk:combo-box-text widget
id -- a string ID for this value, or nil
text -- a string with the text

Appends text to the list of strings stored in the combo box. If the ID is non-nil then it is used as the ID of the row.

This is the same as calling the gtk:combo-box-text-insert function with a position of -1.