I asked ClientCare about this very thing as you are supposed to be able to edit and it's not available (re above: it's a bug).  Their response yesterday:  "The feature you are referring to has actually changed in the system such that in order to change segments, you must change then through the Data...

Hi, We are new clients to SC and I am totally blown away that this isn't already an option.  I understood v15 to be cutting edge and this is a severe hindrance. PLEASE, PLEASE make it an option to allow access to all parts of conversion.  My clients need access to Campaign>Tracking code and 1 eVar (...