have gone and investigated here - you're right (of course) they've changed the interface qhile you're in the build menu to add those + - buttons, and its a much larger interface that therefore isn't properly accessible.
when you said "i have to go to the craft bench to do it." I assumed it was the same interface - it isn't - you don't get the + - buttons in the craft bench - you have to do that right click add / remove thing.