Gtk.ListStore.prototype.insert_before

function insert_before(sibling:Gtk.TreeIter):void {
    // Gjs wrapper for gtk_list_store_insert_before()
}

Inserts a new row before sibling. If sibling is null, then the row will be appended to the end of the list. iter will be changed to point to this new row. The row will be empty after this function is called. To fill in values, you need to call Gtk.set or Gtk.set_value.