The Wolfram Language allows any front end command to be executed programmatically from within the kernel by sending an appropriate front end token. There are tokens for all standard menu commands—as well as ones not accessible directly with the default front end menu configuration.
FrontEndTokenExecute — execute a menu-like command specified by a front end token
"InsertNewGraphic" — insert an empty graphic in the input notebook
"Group" — group selected graphics together
"Ungroup" — ungroup selected graphics
"MoveToFront" — move selected graphics to the front
"MoveToBack" — move selected graphics to the back