Gtk.TreeStore.prototype.insert

function insert(parent:Gtk.TreeIter, position:Number):void {
    // Gjs wrapper for gtk_tree_store_insert()
}

Creates a new row at position. If parent is non-null, then the row will be made a child of parent. Otherwise, the row will be created at the toplevel. If position is -1 or is larger than the number of rows at that level, then the new row will be inserted 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.