Gtk.TreeStore.prototype.insert_before

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

Inserts a new row before sibling. If sibling is null, then the row will be appended to parent 's children. If parent and sibling are null, then the row will be appended to the toplevel. If both sibling and parent are set, then parent must be the parent of sibling. When sibling is set, parent is optional.

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.