Or, just open a Shell after booting Workbench and type:
"ed s:startup-sequence" (without the quotes)
You will see all of the commands that are run, including the SetMap command.
To save your changes, press the ESC key followed by S and A, then press return.
Remember to only work with a copy of your Workbench disk.
ESC and Q will quit back to the shell.
To end the shell, type "endcli".