[RichieTheK]

Thanks to all for your replies. This is what I was looking for.

Originally Posted by Starson17

I like to regularly copy the tweaks file from http://calibre-ebook.com/user_manual...ze.html#tweaks so I can see what tweak options I have available.

Another way is to move the tweaks file to a temporary location. Calibre will then build a new one. You can then edit the new one, referring to the saved copy, to update those tweaks you had previously changed.