[tor-talk] Getting rid of commands in torrc

[bao song]

Sometimes, I wish to access resources only available from IP addresses in a different country from the one where I'm located. So, if the resource is limited to IP addresses in Ptomania, I add

Exitnodes {po}

to my torrc using the Advanced Settings editor.

After I finish, I'd like to remove the 

Exitnodes {po} line from my torrc, but the Advanced Settings editor does not allow this.

Even though I unchecked the 'save settings' when I added the line

Exitnodes {po}

it remains after I stop and restart TBB both on a Macintosh and on Windows.

If I delete the line

Exitnodes {po} and check 'save settings' 

the line remains in my torrc.

I can find no way to get rid of the line.

Can someone explain how I can get rid of lines in my torrc using the Advanced Settings editor (or some other way)?