You can run this command when the simulation mode stops at a breakpoint⮫ «'Online' 'Simulation'»⮫ «'File' 'Printer setup'». You will be given a dialog box with a list of the POU Call Stack.

The first POU is always PLC_PRG, because this is where the executing begins⮫ «POU (program organization unit)».

The last POU is always the POU being executed.

After you have selected a POU and have pressed the 'Go to' button, the selected POU is loaded in its editor, and it will display the line or network being processed.