Robin: He does not want to "hack it" aka edit it directly but override it.
Virgilio: You can still access visual/templatelist directly via url in admin, or re enable Design tab in menu.ini. It was disabled in 4.3 since it is not very well maintained and together with the webshop are going to be moved out as community extensions.
The way it is normally done is to copy the template you want to override to your own extension / design that have higher priority then webin(or the design the original file is in actually), and put the modified template in exactly that location + clear template override cache. Most of us work in teams so we need to version these files using svn / git .. and thus this is the way to go for us.