This command is available in the Extras menu in the task configuration. If the program is stopped at a breakpoint during debugging, it can be used to show the callstack of the corresponding POU. For this purpose the debug task must be selected in the task configuration tree of. The window 'Callstack of task <task name>' will open. There you get the name of the POU and the breakpoint position (e.g. "prog_x (2)" for line 2 of POU prog_x) . Below the complete call stack is shown in backward order. If you press button 'Go To', the focus will jump to that position in the POU which is currently marked in the callstack.