When you are testing your new Google Tag manager tags it could be very usefull if you could customize the value of your cookies. The default way is deleting the cookie and set it again. This is a very time wasting method and not always give the right results.
Therefore Francesco Capano has developed EditThisCookie! Editing cookie values, paths and their experation time is now possible with the EditThisCookie extension for Google Chrome. Install it here.