You can modify the user routines whenever you like.
The system folder and all of the routines held within are read only.
To edit your user routines:
Right click the routine you want to edit and select Edit Routine.
The routine opens in the workspace, where you can modify it.
Once you have adapted the routine to suit your needs, press Ctrl+S to save it.
If you want to reuse a system routine for your own specific needs, see Customizing the system routines.