There is a bug in Google Webmaster Tools right now where you cannot add, edit or delete URL parameters within the interface.
When you access the interface to manage your URL parameters in Webmaster Tools, the buttons to edit or delete or even add parameters is simply not there.
Google's John Mueller is aware of the issue and he said he has reported it to the appropriate team. John wrote:
Thanks for posting. It looks like the buttons have gone missing for you there, sorry! I'll check with the Webmaster Tools team to see what we can do about that.
There is no ETA for a fix.